Novel molecular target for neurotoxicity

ABSTRACT

The present invention relates to the fields of biology, genetics and medicine. In particular it concerns new methods for the detection, characterisation and/or treatment (or management) of neurodegenerative diseases, particularly amyotrophic lateral sclerosis. The invention equally concerns methods for identifying or screening compounds active in these diseases. The invention further concerns the compounds, genes, cells, plasmids or compositions useful for implementing the hereinabove methods. In particular, the invention describes the role of PDE4B in these diseases and its use as a therapeutic, diagnostic or experimental target.

[0001] The present invention relates to the fields of biology, genetics and medicine. In particular it concerns new methods for the detection, characterisation and/or treatment (or management) of neurodegenerative diseases, particularly amyotrophic lateral sclerosis. The invention equally concerns methods for identifying or screening compounds active in these diseases. The invention further concerns the compounds, genes, cells, plasmids or compositions useful for implementing the hereinabove methods. The invention derives notably from the identification of the role of phosphodiesterase 4B in these diseases and describes its use as target or therapeutic, diagnostic or experimental marker in these disorders.

[0002] Many neurodegenerative diseases have been described as having a component or a stage linked to the phenomenon of excitotoxicity. Such is the case for Alzheimer's disease, Parkinson's disease, multiple sclerosis and Huntington's chorea.

[0003] Amyotrophic lateral sclerosis (or ALS) is a neurodegenerative disease accompanied by different types of inclusions such as Lewis bodies and characterised by apoptosis of spinal and cortical motor neurons whose death is sometimes associated with frontal dementia. Sporadic forms for which no mutation has been described exist alongside familial forms (FALS) associated with mutations in the SOD1 gene encoding superoxide dismutase. The majority of cases is sporadic, familial forms (FALS) being very rare. It is likely that a long, asymptomatic period precedes the onset of clinical symptoms, which are variable and difficult to classify. Future advances in therapy will make it possible to replace symptomatic treatments with strategies based on the molecular causes of the disease. At the cellular level, these symptoms are related to death of cortical motor neurons and spinal motor neurons. This neuronal death has been linked to different phenomena which underlie a number of neurodegenerative diseases. Such is the case of excitotoxicity linked to glutamate, oxidative stress, auto-immunity directed against neuronal markers (calcium channels in the case of ALS) as well as cytoskeletal abnormalities. Although such phenomena are known, the cause or causes of these diseases, including ALS, remain obscure. Even though FALS is related to mutations in the SOD1 gene coding for superoxide dismutase, the mechanisms by which neurons become committed towards cellular death, of which at least one component is apoptosis, are unknown.

[0004] Elucidating the molecular events involved in the different phenomena implicated in cell death will allow the development of new therapeutic strategies. The study of these events is difficult to carry out using human biopsy specimens. Such biopsies obviously come from post-mortem samples whose quality is difficult to control and which reflect only the pathological states present at the late stages of the disease.

[0005] Animal models give access to biological samples that allow the different steps of disease development to be analysed and compared with healthy controls. In this respect, transgenic mice expressing the human SOD1 gene bearing one of the mutations prevalent in FALS (mutation G93A) are available from Jackson Laboratory, on condition that a user's licence is obtained from Northwestern University. This model reproduces in 120 days the fatal outcome of the disease with symptoms similar to those in the human disease. The onset of ALS symptoms related to mutation G93A in the SOD1 gene does not result from a reduction in superoxide dismutase activity but rather a gain in function which increases the capacity of the enzyme to generate free radicals. Despite this knowledge, the molecular events governing the different stages of ALS are poorly understood. The complexity of these molecular events reflects the progression of the disease: in the transgenic model studied, no neuronal deregulation or clinical manifestations are observed at 30 days. Sixty days is a stage shortly before symptom onset, but which is already characterised in brain by changes in cellular physiology such as alteration of mitochondrial metabolism, stress and neuronal death associated with an excitotoxicity phenomenon. At 90 days, 50% of cortical and spinal motor neurons are dead and an active process of neuronal apoptosis begins in parallel to an activation of astrocytes. The phenomenon of excitotoxicity is no longer observed at this stage. Neuronal death is associated with activation of caspases which do not appear to be involved in the early stages of the disease.

[0006] Elucidating the different molecular events specific of the different stages of the disease should allow identification of new therapeutic targets as well as new diagnostic markers. One of the most effective approaches to carry out this identification consists in identifying the genes and proteins whose expression characterises a pathophysiological state.

[0007] The present invention now describes the identification of genetic events involved in the phenomena of excitotoxicity and neuronal death. The present invention thus provides new therapeutic and diagnostic approaches to the diseases associated with these phenomena, as well as new targets for identifying active compounds.

[0008] More particularly, a qualitative differential analysis has been carried out on RNA extracted from brain and spinal cord samples without preliminary isolation of neurons in order to take into account a maximum of alternative splicing events related to disease development. This analysis was carried out by qualitative differential screening according to the DATAS method (described in application No. WO99/46403), which has unequalled advantages.

[0009] The present patent application is derived in particular from the applicant's construction of a repertoire of alternative splicings in the brains of 60-day-old animals in the ALS model. This repertoire, which contains more than 200 separate sequences, comprises key players in the excitotoxicity phenomenon, such as potassium channels and the NMDA receptor. Sequences derived from RNAs coding for proteins involved in the response to stress, including heat shock proteins, are also part of this repertoire, underscoring the role of this latter response in the early stages of ALS. Altered energy metabolism clearly appears to affect cortical motor neurons of animals that develop the disease. For instance, intron 6 of mitochondrial creatine kinase is isolated specifically from messenger RNAs expressed in pathological conditions in 60-day-old animals. Interruption of the coding sequence by retention of this intron results in a messenger RNA that encodes an inactive form of the enzyme. This observation agrees with biochemical findings showing a reduction of mitochondrial creatine kinase activity correlated with a reduction in the amount of this enzyme in neurons from animals in the same transgenic model.

[0010] The specificity of the sequences making up this repertoire is confirmed by the fact that the same qualitative differential analysis of gene expression performed in 90-day-old animals leads to a different repertoire in which, in particular, the different markers of excitotoxicity are absent. Analysis of splicing modifications confirms that the molecular events differ according to the stage of the disease.

[0011] In a particularly interesting and unexpected manner, the use of DATAS on RNA from 60-day-old transgenic and control animals has led to the isolation of a cDNA fragment derived from the mRNA of phosphodiesterase 4B. Such fragment corresponds to an exon fragment specifically present in control animals and therefore specifically deleted in SOD1G93A transgenic animals at the 60 day stage. Such fragment spans nucleotides 377 to 486 numbered from the mouse PDE48 stop codon (SEQ ID NO:1) (sequence also accessible in GenBank, No. AF208023). This sequence comprises 2912 bases, the deleted fragment corresponding to bases 2760 to 2869. This is a noncoding region and is differentially expressed in control animals and transgenic animals due to the alternative use of a noncoding 3′ exon or due to the use of two alternative polyadenylation sites. This differential expression has been demonstrated by the RT-PCR experiments presented in FIGS. 1A and 1B.

[0012] The present application therefore demonstrates the involvement of phosphodiesterase 4B in the development of excitotoxicity processes and neuronal death. The results obtained reveal a higher level of expression of PDE4B in pathological nerve tissue, in relation to a structural modification of the corresponding RNA, more particularly the deletion of a region in the 3′ noncoding part. This result is altogether compatible with the presence of mRNA destabilisation sequences in the sequence identified by DATAS. Their deletion in PDE4B mRNA, through splicing or through the use of alternative polyadenylation sequences, can result in stabilisation, therefore in an increased expression of the coding portion of this RNA. This event occurs specifically in the brain of pathological subjects and not in control subjects.

[0013] The present invention therefore describes an original molecular event leading to increased expression of PDE4B mRNA in the brain of pathological subjects and which is correlated over time with the phenomenon of excitotoxicity and/or neuronal death. The invention further shows, for the first time, that increased expression of PDE4B is associated with the early stages of ALS. PDE4B is therefore a new and important therapeutic target in the development of treatments for these diseases, of particular use in the early stages of their development, and addressing the true molecular bases of the disease and not the accompanying symptoms or inflammatory components. The invention also provides for new methods of diagnosis, screening, detection, determination of a predisposition or monitoring the progression or the efficacy of treatment of these diseases.

[0014] Detection, Diagnosis and Screening

[0015] One object of the invention is therefore to provide a method for detecting an excitotoxicity situation or neuronal stress in a subject, comprising measuring in vitro the expression of phosphodiesterase 4, particularly phosphodiesterase 4B, in a sample from the subject. The method advantageously comprises measuring the differential expression of the 3′ noncoding region of the PDE4B gene and the rest of the gene, particularly the coding portion.

[0016] A further object of the invention is therefore to provide a method for detecting an excitotoxicity situation or neuronal stress in a subject, comprising detecting the presence of a mutant RNA of phosphodiesterase 4, particularly phosphodiesterase 4B, in a sample from the subject, in particular a form deleted of all or part of the 3′ noncoding region.

[0017] Another object of the invention is the use of a nucleic acid comprising all or part of a sequence derived from the PDE4B gene or messenger RNA for implementing a method for diagnosis or detection of a situation of neuronal stress and more specifically an excitoxicity situation.

[0018] The invention is generally based on the use of a nucleic acid complementary to all or part of the PDE4B gene or messenger, for detecting pathological events related to excitotoxicity, stress, neuronal death, etc. More generally, the invention provides a method for the diagnosis, screening, characterisation or monitoring of a degenerative disease, comprising demonstrating an alteration in the PDE4 gene or in the corresponding RNA, typically PDE4B.

[0019] The expression of PDE4, or the differential expression, or the presence of an altered form, may be determined by conventional methods of molecular biology, such as for example sequencing, hybridisation, amplification, RT-PCR, gel migration, and the like. The invention has applications in the diagnosis or detection of different pathologies involving excitotoxicity phenomena, such as Alzheimer's disease, Parkinson's disease, multiple sclerosis, ALS, Huntington's chorea or cerebral ischemia. It may be used for early detection, to demonstrate a predisposition, to guide the choice and adaptation of a treatment, to monitor disease progression, etc. It is especially suited to detecting multiple sclerosis or ALS at an early stage.

[0020] To implement the genetic methods of diagnosis or detection according to the invention, one more particularly uses nucleic acids capable of demonstrating a deleted form of PDE4B mRNA, particularly a form deleted of all or part of the 3′ noncoding region. A specific example is the use of a nucleic acid complementary to all or part of the region located between residues 2760 to 2869 of sequence SEQ ID No.: 1, or corresponding residues of the sequence of the human PDE4B gene or mRNA. The cDNA sequence encoding human PDE4B and the corresponding protein are shown in sequences SEQ ID No.: 3 and 4 (also see Genbank, No. NM_(—)002600). The 3′ noncoding region of the human PDE4B gene or RNA corresponds to residues 2461 to 4068 of SEQ ID No.: 3.

[0021] In an advantageous manner, the nucleic acid used (as probe) comprises all or part of the sequence coding for the 3′ noncoding region of the PDE4B gene or RNA located between nucleotides 2384 and 2869 of the sequence SEQ ID NO.: 1 or between nucleotides 2461 and 4068 of the sequence SEQ ID NO: 3 or a sequence complementary thereto.

[0022] According to specific embodiments, the invention makes use of a nucleic acid complementary to a region located within one of the following sequences:

[0023] residues 2384 to 2869 of SEQ ID NO 1

[0024] residues 2500 to 2869 of SEQ ID NO 1

[0025] residues 2760 to 2869 of SEQ ID NO 1

[0026] residues 2780 to 2850 of SEQ ID NO 1

[0027] residues 2790 to 2810 of SEQ ID NO 1

[0028] residues 2600 to 4040 of SEQ ID NO 3

[0029] residues 3000 to 4040 of SEQ ID NO 3

[0030] residues 3500 to 4040 of SEQ ID NO 3

[0031] residues 3900 to 4040 of SEQ ID NO 3.

[0032] In another specific embodiment, one uses a nucleic acid complementary to the sequence of the PDE4 RNA region resulting from deletion of all or part of the 3′ noncoding part. Deletion of a domain in fact creates new junctions in the sequence, which are specific of the deleted form and may be used to demonstrate the presence of such a form in a sample.

[0033] Preferably, the degree of complementarity between the probe and the target sequence is perfect so as to ensure better specificity of hybridisation. However, it is understood that some mispairing may be tolerated. The nucleic acid used for implementation of the hereinabove methods may be a DNA or an RNA, preferably a synthetic DNA. It preferably comprises 10 to 500 bases, typically 10 to 100 bases. It is understood that a longer nucleic acid may be used, if desired, although this is not preferred. The nucleic acid is advantageously a single stranded DNA, from 10 to 500 bases, complementary at least to a region of the 3′ noncoding sequence of PDE4B. The nucleic acid may be labelled, for instance by radioactivity, enzymatic, luminescent, fluorescent, chemical means, etc.

[0034] Another approach for detecting the presence of an alteration in the PDE4 gene makes use of a primer or a nucleic primer pair allowing selective amplification of a portion of PDE4 RNA, preferably comprising a portion of the 3′ noncoding region. One typically uses a primer allowing selective amplification of the altered form of PDE4 RNA, particularly a primer specific of the junction created by deletion of part of the RNA 3′ region.

[0035] In this regard, one object of the invention is based on a primer complementary to a portion of the PDE4B 3′ noncoding region, and allowing amplification of a part of this region. The primer advantageously comprises 8 to 20 bases. It is preferably composed of a fragment of 8 to 20 consecutive residues of the sequence located between nucleotides 2384 and 2869 of sequence SEQ ID NO: 1 or between nucleotides 2461 and 4068 of the sequence SEQ ID NO: 3 or a sequence complementary thereto. A further object of the invention is a primer pair allowing specific amplification of at least part of the PDE4 3′ noncoding region, said pair comprising at least one primer such as defined hereinabove.

[0036] To implement the methods according to the invention, a biological sample from a subject, containing a nucleic acid, is placed in contact in vitro with a nucleic acid (probe, primer, etc.) such as defined hereinabove, and the formation of a hybrid or an amplified product is detected. The biological sample may be a sample of blood, fluid, cell, tissue, etc. The nucleic acid may be immobilised on a support of the type glass, silica, nylon, etc.

[0037] The process of detection, screening or diagnosis may be implemented by using different types of samples from a subject, such as for instance tissue biopsies, particularly nerve tissue. In an especially surprising and advantageous manner, the present invention further shows that deregulation of PDE4 expression, correlated with the excitotoxicity phenomenon, may be directly demonstrated in muscle tissue. This is especially remarkable in the case of neurodegenerative diseases such as ALS.

[0038] During the development of ALS, degenerative phenomena occur not only in brain but also in spinal cord and consequently in muscle through defective innervation. FIG. 2 depicts the modifications of PDE4B mRNA expression in muscle from control and transgenic mice, detected by using the same PCR primers as in the experiment on RNA from the brains of these same animals. In an analogous, but less pronounced manner, a reduction in the expression of the 3′ noncoding region of PDE4B, and not in the remainder of this mRNA (particularly the coding portion), is observed specifically in muscle of animals at the end of the presymptomatic stage, i.e. aged 90 days.

[0039] One difficulty encountered in the study and treatment of ALS is that of establishing an early diagnosis. The observation that PDE4B mRNA is deregulated in ALS muscle makes it possible to establish an early diagnosis from muscle biopsies of patients. Such diagnosis is based on the detection of differential expression between the 3′ noncoding region and the rest of the sequence, particulary the coding portion, of PDE4B.

[0040] A specific method for detecting a situation of neuronal stress, notably excitotoxicity, in particular linked to a neurodegenerative disease in a subject, comprises measuring PDE4B gene expression, or the presence of deleted forms of the PDE4B messenger, in a sample of muscle cells from said subject.

[0041] To measure differential expression, one uses for example a probe corresponding to (that is to say, specific of) a part of the 3′ noncoding region and a probe corresponding to a part of the coding region of PDE4B. The signal detected with each of these probes allows an evaluation of differential expression. Another approach makes use of two primer pairs allowing amplification of a portion of the 3′ noncoding region on the one hand and a portion of the coding region on the other hand.

[0042] An additional object is a kit for analysing PDE4 expression, particularly the differential expression between the 3′ noncoding region and the coding region, the kit comprising a nucleotide probe specific of a part of the sequence of the 3′ noncoding region and a nucleotide probe specific of a part of the sequence of the coding region.

[0043] A further object is a kit for analysing PDE4 expression, particularly the differential expression between the 3′ noncoding region and the coding region, the kit comprising a pair of nucleotide primers allowing specific amplification of at least part of the 3′ noncoding region of PDE4 and a pair of nucleotide primers allowing specific amplification of at least part of the coding region of PDE4.

[0044] Therapy

[0045] Phosphodiesterases hydrolyse cyclic nucleic acids such as cAMP and cGMP, regulating different signalling cascades. PDE4B hydrolyses cAMP, thereby regulating the concentrations of this second messenger inside the cell. The role of cAMP in the balance between cell viability and apoptosis has been well described in the literature. In particular, the cAMP cascade plays an integral role in cell survival cascades involving kinases like Akt and Pl3K as well as in regulating the activity of transcription factor CREB. It is noteworthy that this transcription factor is involved in neuron survival and neurite growth. Nonetheless, the use of PDE and, advantageously, PDE4 inhibitors has never been envisioned to improve neuron viability and more particularly to protect them against excitotoxicity. It has been suggested that PDE4 inhibitors, developed to inhibit inflammatory phenomena, may potentially be useful in neurodegenerative diseases such as Alzheimer's disease. This suggestion is based on the goal of reducing the inflammation observed in brain during neurodegenerative processes and not at all on a rationale aiming to directly inhibit neuronal death.

[0046] The present invention demonstrates the existence of splicing events and alternative polyadenylation sites affecting the PDE4B gene, associated with the development of neuronal excitotoxicity, and provides the molecular basis that justifies the use of PDE4 inhibitors for the treatment of ALS and more generally for improvement of neuron viability during excitotoxicity phenomena, in particular starting from the early stages of these diseases.

[0047] Another object of the invention is therefore based on the use of a compound capable of inhibiting or reducing the expression or activity of PDE4B, in order to prepare a composition designed to treat neurodegenerative diseases, notably in early stages, more preferably to reduce the early neuronal excitotoxicity associated with neurodegenerative diseases such as ALS, Alzheimer's disease or Parkinson's disease.

[0048] A particular object consists in the use of a PDE4 inhibitor for preparing a composition designed to treat ALS, particularly to reduce excitotoxicity in subjects with ALS or to increase neuron survival in subjects with ALS.

[0049] Another object of the invention is the use of a compound capable of inhibiting (preferably in a selective manner) the expression or activity of PDE4B of sequence SEQ ID NO: 2 or 4 in order to prepare a composition designed to reduce neuronal excitotoxicity.

[0050] A further object of the invention is a method for treating a disease associated with neuronal stress, particularly excitotoxicity, comprising administering to a subject a compound that inhibits PDE4B activity or expression, preferably a compound that selectively inhibits PDE4.

[0051] Another object of the invention is based on a method for treating ALS, particularly a method for increasing neuron survival in subjects with ALS, comprising administering to a subject a PDE4 inhibitor, preferably a compound that selectively inhibits PDE4.

[0052] Within the context of the invention, the term “treatment” refers to preventive, curative, palliative treatment, as well as management of patients (alleviating suffering, improving life expectancy, slowing disease progression), etc. The treatment may furthermore be conducted in combination with other agents or treatments, especially addressing late events in the disease, such as caspase inhibitors or other active compounds.

[0053] The compound used may be any compound that can inhibit the expression of PDE4, particularly PDE4B, that is to say, in particular any compound inhibiting gene transcription, RNA maturation, mRNA translation, posttranslational protein modification, etc. It may be a compound inhibiting RNA modification, particularly the deletion of part of the 3′ noncoding region.

[0054] In a specific embodiment, the compound is an antisense nucleic acid, capable of inhibiting transcription of the PDE4B gene or translation of the corresponding mRNA. The antisense nucleic acid may comprise all or part of the sequence of the PDE4B gene, a fragment thereof, the PDE4B messenger, or a sequence complementary thereto. The antisense nucleic acid may notably comprise a region complementary to the sequence located between residues 218 to 2383 of SEQ ID NO:1 or 766 to 2460 of SEQ ID NO: 3, and inhibit (or reduce) its translation into protein. The antisense nucleic acid may be a DNA, an RNA, a ribozyme, etc. It may be single-stranded or double-stranded. It may also be an RNA encoded by an antisense gene. Where it is an antisense oligonucleotide, it typically contains fewer than 100 bases, for example on the order of 10 to 50 bases. Such oligonucleotide may be modified to improve its stability, its resistance to nucleases, its penetration into the cell, etc.

[0055] According to a further embodiment, the compound is a peptide, for example comprising a region of the PDE4 protein (particularly PDE4B) and able to antagonise its activity.

[0056] According to another embodiment, the compound is a chemical compound of natural or synthetic origin, particularly an organic or inorganic molecule, of plant, bacterial, viral, animal, eukaryotic, synthetic or semi-synthetic origin, capable of modulating the expression or activity of PDE4B.

[0057] In a preferred variant, the compound is a synthetic compound that inhibits PDE4. Different types of inhibitors may be used. Preferably they are compounds from the pyrazolopyridine family, among which a specific example is etazolate, or compounds from the family of xanthine (or 2,6-dioxopurine) derivatives, including in particular pentoxifylline.

[0058] Compounds from the pyrazolopyridine family are chosen in particular from among the following compounds:

[0059] Etazolate which has the following formula:

[0060] 4-butylamino-1-ethyl-6-methyl-1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid ethyl ester (tracazolate),

[0061] 4-butylamino-1-ethyl-1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid ethyl ester,

[0062] 1-(4-amino-pyrazolo[3,4-b]pyridin-1-yl)-β-D-1-deoxy-ribofuranose,

[0063] 1-ethyl-4-(N′-isopropylidene-hydrazino)-1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid ethyl ester (SQ 20009),

[0064] 4-amino-6-methyl-1-n-pentyl-1H-pyrazolo[3,4-b]pyridine,

[0065] 4-amino-1-ethyl-6-methyl-1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid ethyl ester (desbutyl tracacolate),

[0066] 4-amino-1-pentyl-1H-pyrazolo[3,4-b]pyridine-5-carboxamide,

[0067] 1-ethyl-6-methyl-4-methylamino-1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid ethyl ester,

[0068] 4-amino-6-methyl-1-propyl-1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid ethyl ester,

[0069] 1-ethyl-4-ethylamino-6-methyl-1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid ethyl ester,

[0070] 4-amino-1-butyl-6-methyl-1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid ethyl ester,

[0071] 5-(4-amino-pyrazolo[3,4-b]pyridin-1-yl)-2-hydroxymethyl-tetrahydro-furan-3-ol,

[0072] 1-allyl-4-amino-6-methyl-1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid allyl ester,

[0073] 4-amino-6-methyl-1-pentyl-1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid,

[0074] 4-amino-1-ethyl-3,6-dimethyl-1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid ethyl ester,

[0075] 4-dimethylamino-1-ethyl-6-methyl-1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid ethyl ester,

[0076] 1-ethyl-6-methyl-4-propylamino-1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid ethyl ester,

[0077] 4-amino-1-pentyl-1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid ethyl ester,

[0078] 4-amino-6-methyl-1-pent-4-ynyl-1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid ethyl ester,

[0079] 4-amino-1-but-3-enyl-1H-pyrazolo[3,4-b]pyridine-5-allylamide,

[0080] 4-amino-1-pentyl-1H-pyrazolo[3,4-b]pyridine-5-isopropylamide,

[0081] 4-amino-1-pentyl-N-n-propyl-1H-pyrazolo-[3,4-b]pyridine-5-carboxamide,

[0082] 4-amino-1-butyl-6-methyl-1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid allyl ester,

[0083] 4-amino-6-methyl-1-pent-3-ynyl-1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid ethyl ester,

[0084] 4-amino-1-pentyl-1H-pyrazolo[3,4-b]pyridine-5-prop-2-ynylamide,

[0085] 4-amino-1-(3-methyl-butyl)-1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid allyl ester,

[0086] 4-amino-1-pentyl-1H-pyrazolo<3,4-b>pyridine-5-N-(2-propenyl)carboxamide,

[0087] 4-amino-1-pentyl-1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid allyl ester,

[0088] 4-amino-1-pentyl-1H-pyrazolo[3,4-b]pyridine-5-butylamide,

[0089] 4-amino-1-but-3-ynyl-6-methyl-1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid allyl ester,

[0090] 4-amino-1-but-3-enyl-6-methyl-1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid allyl ester,

[0091] 4-amino-6-methyl-1-pentyl-1H-pyrazolo[3,4-b]pyridine-5-allylamide,

[0092] 4-amino-6-methyl-1-pentyl-1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid allyl ester,

[0093] 4-amino-6-methyl-1-(3-methyl-butyl)-1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid allyl ester,

[0094] 4-amino-6-methyl-1-pentyl-1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid isobutyl ester,

[0095] 4-amino-6-methyl-1-pentyl-1H-pyrazolo[3,4-b]pyridine-5-butylamide,

[0096] 4-amino-6-methyl-1-(3-methyl-but-2-enyl)-1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid allyl ester,

[0097] 4-amino-1-pentyl-1H-pyrazolo[3,4-b]pyridine-5-cyclopropylamide,

[0098] ethyl 4-amino-1-pentyl-1H-pyrazolo[3,4-b]pyridine-5-hydroxamate,

[0099] 4-amino-6-methyl-1-pentyl-1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid prop-2-ynyl ester,

[0100] 4-amino-6-methyl-1-pent-4-ynyl-1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid allyl ester,

[0101] 4-amino-6-methyl-1-pent-4-enyl-1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid allyl ester,

[0102] 4-amino-1-pent-3-ynyl-1H-pyrazolo[3,4-b]pyridine-5-propylamide,

[0103] 4-amino-1-pentyl-1H-pyrazolo[3,4-b]pyridine-5-cyclopropylmethyl-amide,

[0104] 4-amino-6-methyl-1-pentyl-1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid 2-methyl-allyl ester,

[0105] 4-amino-1-pent-3-ynyl-1H-pyrazolo[3,4-b]pyridine-5-allylamide (ICI 190,622),

[0106] 4-amino-1-pent-4-ynyl-N-2-propenyl-1H-pyrazolo[3,4-b]pyridine-5-carboxamide,

[0107] 4-amino-1-pent-3-ynyl-1H-pyrazolo[3,4-b]pyridine-5-prop-2-ynylamide,

[0108] 4-amino-1-pentyl-1H-pyrazolo[3,4-b]pyridine-5-but-2-ynylamide,

[0109] 4-amino-6-methyl-1-pent-3-ynyl-1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid allyl ester,

[0110] 4-amino-1-(2-cyclopropyl-ethyl)-6-methyl-1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid allyl ester,

[0111] 4-amino-1-hex-5-ynyl-6-methyl-1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid allyl ester,

[0112] 4-amino-1-pent-3-ynyl-1H-pyrazolo[3,4-b]pyridine-5-cyclopropylmethyl-amide,

[0113] 4-amino-6-methyl-1-pentyl-1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid but-3-enyl ester,

[0114] 4-amino-6-methyl-1-pentyl-1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid cyclopropylmethyl ester,

[0115] 4-butylamino-1-pentyl-1H-pyrazolo[3,4-b]pyridine-5-allylamide,

[0116] 4-amino-6-methyl-1-pentyl-1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid 2-cyclopropyl-ethyl ester,

[0117] 4-amino-6-methyl-1-pent-3-ynyl-1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid cyclopropylmethyl ester,

[0118] 4-amino-6-methyl-1-pent-4-ynyl-1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid cyclopropylmethyl ester,

[0119] 4-amino-1-benzyl-6-methyl-1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid ethyl ester,

[0120] 4-amino-1-pentyl-1H-pyrazolo[3,4-b]pyridine-5-benzylamide,

[0121] 4-amino-1-pentyl-1H-pyrazolo[3,4-b]pyridine-5-phenylamide,

[0122] 4-amino-6-methyl-1-pentyl-1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid benzyl ester,

[0123] 4-azido-1-β-D-ribofuranosylpyrazolo[3,4-b]pyridine,

[0124] 1-pent-3-ynyl-N-2-propenyl-4-propionamido-1H-pyrazolo[3,4-b]pyridine-5-carboxamide,

[0125] 2-(4-amino-pyrazolo[3,4-b]pyridin-1-yl)-5-hydroxymethyl-tetrahydro-furan-3,4-diol,

[0126] 2-(6-methyl-1H-pyrazolo[3,4-b]pyridin-4-ylamino)-ethanol,

[0127] 3-(6-methyl-1H-pyrazolo[3,4-b]pyridin-4-ylamino)-propan-1-ol,

[0128] 3-(6-methyl-1H-pyrazolo[3,4-b]pyridin-4-ylamino)-acetic acid propyl ester,

[0129] 2-(6-methyl-1H-pyrazolo[3,4-b]pyridin-4-ylamino)-propionic acid ethyl ester,

[0130] 2-(6-methyl-1H-pyrazolo[3,4-b]pyridin-4-ylamino)-pentanoic acid ethyl ester,

[0131] 2-(6-methyl-1H-pyrazolo[3,4-b]pyridin-4-ylamino)-benzoic acid ethyl ester,

[0132] 3-(6-methyl-1H-pyrazolo[3,4-b]pyridin-4-ylamino)-pentanoic acid propyl ester,

[0133] N-benzylidene-N′-(3-methyl-1-phenyl-1H-pyrazolo[3,4-b]pyridin-4-yl)-hydrazine,

[0134] N-furan-2-ylmethylene-N′-(3-methyl-1-phenyl-1H-pyrazolo[3,4-b]pyridin-4-yl)-hydrazine,

[0135] N-(4-fluoro-benzylidene)-N′-(3-methyl-1-phenyl-1H-pyrazolo[3,4-b]pyridin-4-yl)-hydrazine,

[0136] N-(3-furan-2-yl-allylidene)-N′-(3-methyl-1-phenyl-1H-pyrazolo[3,4-b]pyridin-4-yl)-hydrazine,

[0137] N-(4-methoxy-benzylidene)-N′-(3-methyl-1-phenyl-1H-pyrazolo[3,4-b]pyridin-4-yl)-hydrazine,

[0138] 4-[(3-methyl-1-phenyl-1H-pyrazolo[3,4-b]pyridin-4-yl)-hydrazonomethyl]-benzonitrile,

[0139] N-benzo[1,3]dioxol-5-ylmethylene-N′-(3-methyl-1-phenyl-1H-pyrazolo[3,4-b]pyridin-4-yl)-hydrazine,

[0140] N-(3-methyl-1-phenyl-1H-pyrazolo[3,4-b]pyridin-4-yl)-N′-(4-nitro-benzylidene)-hydrazine,

[0141] N-(3-methyl-1-phenyl-1H-pyrazolo[3,4-b]pyridin-4-yl)-N′-(2-nitro-benzylidene)-hydrazine,

[0142] N-(3-methyl-1-phenyl-1H-pyrazolo[3,4-b]pyridin-4-yl)-N′-(4-trifluoromethyl-benzylidene)-hydrazine,

[0143] N-(3-methyl-1-phenyl-1H-pyrazolo[3,4-b]pyridin-4-yl)-N′-(5-nitro-furan-2-ylmethylene)-hydrazine,

[0144] N-(3-methyl-1-phenyl-1H-pyrazolo[3,4-b]pyridin-4-yl)-N′-(2-trifluoromethyl-benzylidene)-hydrazine,

[0145] N-(3-methyl-1-phenyl-1H-pyrazolo[3,4-b]pyridin-4-yl)-N′-(6-nitro-benzo[1,3]dioxol-5-ylmethylene)-hydrazine,

[0146] 4-(3-chloro-4-methoxy-benzylamino)-1-ethyl-1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid,

[0147] 4-(3-chloro-4-methoxy-benzylamino)-1-ethyl-1H-pyrazolo[3,4-b]pyridine-5-(pyridin-4-ylmethyl)-amide,

[0148] 4-(3-chloro-4-methoxy-benzylamino)-1-ethyl-1H-pyrazolo[3,4-b]pyridine-5-(tetrahydro-furan-2-ylmethyl)-amide,

[0149] 4-(3-chloro-4-methoxy-benzylamino)-1-ethyl-1H-pyrazolo[3,4-b]pyridine-5-(5-hydroxy-pentyl)-amide,

[0150] 4-(3-chloro-4-methoxy-benzylamino)-1-ethyl-1H-pyrazolo[3,4-b]pyridine-5-[3-(2-oxo-pyrrolidin-1-yl)-propyl]-amide,

[0151] 4-tert-butylamino-1-(2-chloro-2-phenyl-ethyl)-1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid ethyl ester,

[0152] 1-(2-chloro-2-phenyl-ethyl)-4-cyclopropylamino-1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid ethyl ester,

[0153] 1-(2-chloro-2-phenyl-ethyl)-4-propylamino-1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid ethyl ester,

[0154] 1-(2-chloro-2-phenyl-ethyl)-4-phenylamino-1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid ethyl ester,

[0155] 4-butylamino-1-(2-chloro-2-phenyl-ethyl)-1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid ethyl ester,

[0156] 1-(2-chloro-2-phenyl-ethyl)-4-(2-ethoxy-ethylamino)-1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid ethyl ester,

[0157] 4-benzylamino-1-(2-chloro-2-phenyl-ethyl)-1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid ethyl ester,

[0158] 1-(2-chloro-2-phenyl-ethyl)-4-phenethylamino-1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid ethyl ester,

[0159] Among the xanthine derivatives, one uses in particular (i) the (ω-1)-hydroxyalkyl-dialkylxanthines wherein the (ω-1)-hydroxyalkyl group contains 5 or 6 carbon atoms and is in position 1 or 7, the alkyl group in the other position 7 or 1 contains 1 to 12 carbon atoms and the alkyl group in position 3 contains 1 to 4 carbon atoms, (ii) the (ω-1)-oxoalkyl-dimethylxanthines wherein the (ω-1)-oxoalkyl group contains 5 or 6 carbon atoms and is in position 1 or 7, or (iii) derivatives of dimethylxanthine having an alkyl group containing from 4 to 12 carbon atoms or a benzyl group in position 1 or 7.

[0160] Typically, the oxoalkyl-dialkylxanthines include for example 1-(5-oxohexyl)-3,7- and 7-(5-oxohexyl)-1,3-dimethylxanthines. Other xanthines may also be used, such as in particular the 3,7-dimethylxanthines and 1,3-dimethylxanthines substituted with a butyl, isoamyl, hexyl, lauryl or benzyl group in position 1 or 7, as well as the homologues of these compounds with a hydroxy or oxo group in position (ω-1)-position, for example 1-(4-hydroxypentyl)- and 1-(5-hydroxyhexyl)-3,7-dimethylxanthines, 7-(4-hydroxypentyl)- and 7-(5-hydroxyhexyl)-1,3-dimethylxanthines, 1-(4-oxopentyl)-, 1-(5-oxohexyl)-, 1-(2-methyl-3-oxobutyl)- and 1-(2-ethyl-3-oxobutyl)-3,7-dimethylxanthines and the corresponding 1,3-dimethyl compounds having a (ω-1)-hydroxyalkyl or (ω-1)-oxoalkyl group in position 7. Homologues of the abovementioned hydroxyalkyl-dimethylxanthines are those having in position 1 or 7 which is not occupied by a hydroxyalkyl group, instead of a methyl group, an alkyl group having 2 to 12 carbon atoms, such as 1-ethyl-, 1-propyl-, 1-butyl- and 1-isobutyl-3-methyl-7-(5-hydroxyhexyl)-xanthines and 7-ethyl-, 7-propyl-, 7-butyl- and 7-isobutyl-1-(5-hydroxyhexyl)-3-methylxanthines, and the corresponding compounds having instead of a methyl group in position an alkyl group containing 2 to 4 carbon atoms, such as in particular an ethyl, n-propyl, isopropyl, isobutyl or n-butyl group.

[0161] Among such xanthine derivatives, one uses in particular pentoxifylline which has the following formula:

[0162] The present invention therefore proposes, for the first time, PDE4B as a therapeutic target for the treatment of molecular events associated with excitotoxicity. According to specific embodiments, the invention may be used to inhibit or reduce neuronal excitotoxicity in early stages of neurodegenerative diseases. It finds applications particularly in the treatment of Alzheimer's disease, Parkinson's disease, multiple sclerosis, ALS, Huntington's chorea and cerebral ischemia.

[0163] Other objects of the invention are based on:

[0164] use of the hereinabove compounds, particularly etazolate or pentoxifylline, for the treatment of ALS, notably to reduce neuronal excitotoxicity in the early stage of ALS, or

[0165] use of the hereinabove compounds, particularly pentoxifylline or etazolate, for preparing a composition designed to inhibit PDE4B activity in patients with ALS.

[0166] The invention equally concerns methods for treating ALS comprising administering a compound that selectively inhibits the expression or activity of PDE4B of sequence SEQ ID NO: 2 or 4. Preferably, the methods of the invention are used for treatment in the early stage of neurodegenerative diseases.

[0167] The administration may be performed by any method known to those skilled in the art, preferably by the oral route or by injection, typically by the intraperitoneal, intracerebral, intravenous, intraarterial or intramuscular route. Administration by the oral route is preferred. The administered doses may be adapted by those skilled in the art. Typically, approximately 0.01 mg to 100 mg/kg are injected, for inhibitor compounds that are chemical in nature. For nucleic compounds, doses may range for example from 0.01 mg to 100 mg per dose. It is understood that repeated injections may be given, possibly in combination with other active agents or any pharmaceutically acceptable vehicle (eg., buffers, isotonic saline solutions, in the presence of stabilisers, etc.).

[0168] The invention may be used in mammals, notably in human beings. The results presented in the examples illustrate the efficacy of PDE4B inhibitors in improving the viability of neurons placed in excitotoxicity conditions.

[0169] Methods of Selection and Tools

[0170] Other objects of the invention concern methods for selecting, identifying or characterising compounds active in diseases associated with excitotoxicity, or neuronal stress, comprising placing test compounds in contact with a cell expressing PDE4B (particularly a variant devoid of the 3′ noncoding region), and identifying compounds inhibiting the expression or activity of this protein.

[0171] The methods may be used with different cell populations, such as primary cells or cell lines of mammalian origin (human, murine, etc.). Advantageously, cells which do not naturally express PDE4B, transfected with a nucleic acid coding the desired variant, are used. In this manner, the selectivity of the method is increased. Lower eukaryotic cells (yeasts, etc.) or prokaryotic cells may also be used.

[0172] The screening methods may also be carried out in an acellular system, by measuring the capacity of test compounds to bind PDE4B or a variant or fragment thereof.

[0173] Another object of the invention concerns any nucleic acid coding a polypeptide such as defined hereinabove, vectors containing it, recombinant cells, and utilisations. The vectors may be plasmids, phages, cosmids, viruses, artificial chromosomes, etc. Preferred vectors are exemplified by plasmid vectors, such as those derived from commercially available plasmids (pUC, pcDNA, pBR, etc.). Such vectors advantageously contain a selection gene and/or an origin of replication and/or a transcriptional promoter. Other specific vectors are for example viruses or phages, particularly replication-defective recombinant viruses, such as viruses derived from retroviruses, adenoviruses, AAV, herpes virus, baculovirus, etc. The vectors may be used in any competent host, such as for example prokaryotic or eukaryotic cells. These may be bacteria (E. coli for example), yeasts (Saccharomyces or Kluyveromyces, for example), plant cells, insect cells, mammalian cells, notably human, etc. These may be cell lines, primary cells, mixed cultures, etc.

[0174] Other aspects and advantages of the present invention will become apparent from the following examples which are given for purposes of illustration and not by way of limitation.

LEGENDS OF FIGURES

[0175]FIG. 1: Semi-quantitative PCR of PDE4B on brain (1A) and muscle (1B) specimens.

[0176]FIG. 2: Pentoxifylline protects primary neurons against formation of cerebellar granules related to excitotoxicity induced by kainate.

[0177]FIG. 3: Pentoxifylline protects primary neurons against formation of cerebellar granules related to excitotoxicity induced by NMDA/serine.

[0178]FIG. 4: Neuroprotective effect of etazolate against toxicity induced by NMDA/serine on brain granular cells.

[0179]FIG. 5: Neuroprotective effect of etazolate against toxicity induced by kainate on brain granular cells.

[0180]FIG. 6: Neuroprotective effect of pentoxifylline against toxicity induced by NMDA/serine on cortical neurons.

[0181]FIG. 7: Neuroprotective effect of pentoxifylline against toxicity induced by kainate on cortical neurons.

[0182]FIG. 8: Neuroprotective effect of etazolate against toxicity induced by NMDA/serine on cortical neurons.

[0183]FIG. 9: Neuroprotective effect of etazolate against toxicity induced by kainate on cortical neurons.

[0184]FIG. 10: Neuroprotective effect of 8-bromo-cAMP against toxicity induced by NMDA/serine on brain granular cells.

[0185]FIG. 11: Neuroprotective effect of 8-bromo-cAMP against toxicity induced by kainate on brain granular cells.

EXAMPLES Example 1 Identification of PDE4 as Molecular Target of Excitotoxicity

[0186] Qualitative differential analysis was carried out on polyadenylated (poly A+) RNA extracted from brain specimens of animals at different stages, without preliminary isolation of neurons so as to take into account a maximum of alternative splicing events linked to disease development.

[0187] Poly A+ RNAs are prepared by methods known to those skilled in the art. In particular, this may be a treatment by means of chaotropic agents such as guanidium thiocyanate followed by extraction of total RNA by means of solvents (phenol, chloroform for example). Such methods are well known to those skilled in the art [see Maniatis et al., Chomczynsli et al., Anal. Biochem. 162 (1987) 156], and may be easily practised by using commercially available kits. Poly A+ RNAs are prepared from these total RNAs according to conventional methods known to those skilled in the art and provided in commercially available kits.

[0188] These poly A+ RNAs serve as template for reverse transcription reactions using reverse transcriptase. In an advantageous manner, reverse transcriptases devoid of RNase H activity are used, so as to obtain first complementary DNA strands that are larger in size than those obtained with conventional reverse transcriptases. Such RNase H-free reverse transcriptase preparations are commercially available.

[0189] At each time point in disease development (30 days, 60 days and 90 days), the poly A+ RNAs as well as the single-stranded cDNAs are prepared from transgenic animals (T) and syngeneic control animals (C).

[0190] In accordance with the DATAS method, for each time point hybridisations are carried out of mRNA (C) with cDNA (T), and reciprocal hybridisations of mRNA (T) with cDNA (C).

[0191] The mRNA/cDNA heteroduplexes are then purified according to the protocols of the DATAS method.

[0192] RNA sequences not paired with a complementary DNA are released from these heteroduplexes through the action of RNAse H, as this enzyme degrades paired RNA sequences. Such unpaired sequences represent qualitative differences existing between RNAs which by the way are homologous between themselves. These qualitative differences may be located anywhere on the RNA sequence, at the 5′ or 3′ region or inside the sequence and notably in the coding sequence. Depending on their location, these sequences may not only be alternative splicings, but also may be the result of translocations or deletions.

[0193] The RNA sequences representing qualitative differences are then cloned according to methods known to those skilled in the art and more specifically those described in the patent for the DATAS method.

[0194] Such sequences are entered into cDNA banks which constitute qualitative differential banks. One such bank contains the exons and introns specific of the healthy situation; the other banks contain the splicing events characteristic of pathological conditions.

[0195] Differential expression of the clones was checked by hybridisation with probes obtained by reverse transcription of messenger RNAs extracted from the different situations under study. Clones showing differential hybridisation were retained for subsequent analysis. The sequences identified by DATAS correspond to introns and/or exons differentially expressed through splicing in pathological situations and in the healthy situation. These splicing events may be specific of a given stage in the development of the disease or characteristic of the healthy state.

[0196] Comparison of these sequences with databases makes it possible to classify the information obtained and propose a reasoned selection of sequences according to their diagnostic or therapeutic interest.

[0197] The performance of DATAS on RNAs from 60-day-old transgenic and control animals has led to the isolation of a cDNA fragment derived from phosphodiesterase 4B mRNA. This fragment corresponds to an exon fragment specifically present in control animals and therefore specifically deleted in SOD1G93A transgenic animals at the 60-day stage. The fragment covers nucleotides 377 to 486 numbered from the stop codon of murine PDE4B (SEQ ID NO:1). This sequence comprises 2912 bases, the deleted fragment corresponding to bases 2760 to 2869. This region is noncoding and is expressed differentially between control animals and transgenic animals, due to alternative use of a 3′ noncoding exon or due to the use of two alternative polyadenylation sites.

Example 2 RT-PCR Experiments: Confirmation of Differential Expression

[0198] Differential expression of PDE4B in a situation of neuronal stress, as compared to a reference situation, was verified by the RT-PCR experiments described in FIG. 1.

[0199] These experiments were conducted according to methods well known to those skilled in the art and made it possible to follow the expressions of two distinct regions of PDE4B mRNA. One such region spans the initiation codon of this mRNA (PDE4B 5′), the other partly spans the fragment identified by the DATAS method (PDE4B DATAS). The locations of the PCR primers used are indicated in FIG. 1.

[0200] PO RNA is a ribosomal RNA serving as internal control to check that the same amount of RNA was used for each experimental point. Analyses were performed with RNA extracted from control (C) and transgenic (T) animals aged 30, 60 and 90 days, i.e. before onset of pathological symptoms.

[0201] Total RNAs from the brains of control or SOD1 G93A mice aged 30, 60 or 90 days were transcribed to cDNA using the standard Superscript™ protocol (Invitrogen). For semi-quantitative PCR the reverse transcription reaction products were diluted ten-fold. The specific primers of the DATAS fragment correspond to nucleotides 2526 to 2545 for the sense strand (5′ GCC AGG CCG TGA AGC AAA TA 3′; SEQ ID NO: 5), and to nucleotides 2790 to 2807 for the antisense strand (5′ TCA MG ACG CGA AAA CAT 3′; SEQ ID NO: 6) and for the more 3 prime fragment the primers correspond to nucleotides 145 to 165 for the sense strand (5′ CCG CGT CAG TGC CTT TGC TAT 3′; SEQ ID NO: 7), and to nucleotides 426 to 404 for the antisense strand (5′ CGC TGT CGG ATG CTT TTA TTC AC 3′; SEQ ID NO: 8). The P0 gene was used as reference and amplified by the following primers: sense strand: 5′ TCG CTT TCT GGA GGG TGT C 3′ (SEQ ID NO: 9) and antisense strand: CCG CAG GGG CAG CAG TGG 3′ (SEQ ID NO:10).

[0202] Amplification was achieved by 30 PCR cycles as follows:

[0203] 30 seconds at 94° C.

[0204] 1 minute at 57° C.

[0205] 30 seconds at 72° C., followed by a cycle of 2 minutes at 72° C.

[0206] The different PCR products were loaded on a 1.5% agarose gel. The experience was carried out in triplicate with two different reverse transcription reactions.

[0207]FIG. 1 shows the results obtained from RNAs extracted from brain or muscle of the animals.

[0208] Whereas the same quantity of cDNA is amplified from PO RNA in all samples, variations are seen with PDE4B mRNA. The most significant variations are detected in the 90-day-old animals: while an increase in the expression of the PDE4 5′ fragment is observed in brain of transgenic animals, a very strong decrease in PDE4B (DATAS) expression occurs in the brain of transgenic animals.

[0209] This finding establishes a correlation between the decrease in expression of a 3′ noncoding mRNA fragment of PDE4B and the increase in expression of the 5′ coding region of this same messenger. This result is altogether compatible with the presence of mRNA destabilising sequences in the sequence identified by DATAS and demonstrates the correlation between PDE4B expression and the phenomenon of excitotoxicity.

Example 3 Inhibition of Excitotoxicity by Inhibitors of PDE4

[0210] For this example, rat brain granular as well as cortical neurons were cultured according to techniques known to those skilled in the art.

[0211] Primary Rat Brain Granular Cell Cultures:

[0212] Seven-day-old Wistar rats were decapitated and their brains dissected. After removing the meninges, the tissue was cut into small pieces and trypsinized for 15 minutes at 37° C. The cells were dissociated in a grinder and seeded at a density of 300,000 cells per cm² into basic Eagle medium supplemented with 10% fetal calf serum and 2 mM glutamine. The next day, 10 μM ARA-C, an antimitotic agent, was added to inhibit the growth of glial cells. After nine days of culture, cells were treated with the phosphodiesterase inhibitors pentoxifylline and etazolate, three hours before adding the toxins 50 μM kainate or 100 μm N-methyl-D-aspartate in the presence of 10 μM D-serine. 8-bromo-cAMP was added immediately before the toxins. All treatments were performed at least in duplicate and in at least two different cultures. After a 6 hour incubation, toxicity was evaluated by an MTT test. The results, normalized to the mean of untreated controls, were analysed statistically with a Wilcoxon test. The level of significance was set at p<0.05.

[0213] Primary Cortical Cell Cultures:

[0214] Sixteen-day-old embryos from Wistar rats were removed and the cortex dissected. After trypsinization for 25 minutes at 37° C., the cells were dissociated in a grinder, then seeded at a density of 300,000 cells per cm² into minimum essential medium supplemented with 10% horse serum, 10% fetal calf serum and 2 mM glutamine. After four days of culture, half of the medium was replaced by minimum essential medium supplemented with 5% horse serum and 2 mM glutamine. On the same day, 10 μM 5-fluoro-2-deoxyuridine, an antimitotic agent, was added. After 7 and 11 days of culture, half of the medium was replaced by conditioned medium composed of MEM supplemented with 5% horse serum and 2 mM glutamine; this medium was passed overnight on a layer of cortical astrocytes before use. On day 14, cells were treated with the phosphodiesterase inhibitors pentoxifylline and etazolate 1 hour before adding the toxins 50 μM kainate or 20 μM N-methyl-D-aspartate in the presence of 10 μM D-serine. All treatments were performed at least in duplicate and in at least two different cultures. After a 6 hour incubation, toxicity was evaluated by an MTT test. The results, normalized to the mean of untreated controls, were analysed statistically with a Wilcoxon test. The level of significance was set at p<0.05.

[0215] MTT:

[0216] Toxicity was measured with an MTT test. After incubation with the compounds, MTT was added at 0.5 mg/ml final concentration per well. Plates were then incubated for 30 minutes at 37° C. in the dark. The medium was aspirated and the crystals resuspended in 500 μl of DMSO (dimethylsulfoxide). Absorbance at 550 nm was read and the percentage viability was calculated.

[0217] Results:

[0218] The results are presented in FIGS. 2 to 10. These results illustrate the protective effect of the compounds according to the invention on neuron survival. When neurons were cotreated with a PDE4 inhibitor, a dose-dependent protective effect was observed with both excitotoxicity inducers (NMDA/serine and kainate). Such a protective effect was observed with pentoxifylline and etazolate.

[0219]FIGS. 2 and 3 show the results obtained with pentoxifylline on brain granular cells. They show that pentoxifylline affords 43% protection of these cells in the case of NMDA/serine treatment, and 33% in the case of kainate-induced toxicity.

[0220]FIGS. 4 and 5 present the results obtained with etazolate on brain granular cells. They show that etazolate gives 60% protection of these cells in the case of NMDA/serine treatment, and 57% in the case of kainate-induced toxicity.

[0221]FIGS. 6 and 7 show the results obtained with pentoxifylline on cortical neurons. They show that pentoxifylline affords a 50% protective effect on these cells in the case of NMDA/serine treatment, and 66% in the case of kainate-induced toxicity.

[0222]FIGS. 8 and 9 give the results obtained with etozalate on cortical neurons. They show that etozalate provides 33% protection of these cells in the case of NMDA/serine treatment, and 25% in the case of kainate-induced toxicity.

[0223] The relevance of this protection is confirmed by the percent of protection achieved with increasing concentrations of cAMP, a PDE substrate, given as an example for brain granular cells in FIGS. 10 and 11. A 40% protection was observed for NMDA/serine treatment and 40% with kainate treatment.

[0224] The present invention therefore not only demonstrates the involvement of PDE4B in mechanisms of excitotoxicity, particularly in an ALS model, but also demonstrates the ability of PDE4 inhibitors to preserve neuronal viability during stress linked to excitotoxicity.

Example 4 Clinical use in Man

[0225] This example describes the conditions of human clinical use of a PDE4 inhibitor in the treatment of ALS. This example illustrates the therapeutic potential of the invention and its conditions of implementation in man.

[0226] In this clinical trial, treatment is based on a combination of pentoxifylline and riluzole, the former at a dose of 400 mg three times a day, for a total daily dose of 1200 mg. Pentoxifylline is administered as a tablet formulation. This is a multicenter, double-blind, placebo-controlled trial in 400 patients comprising men and women aged 18 to 80 years, presenting with sporadic or familial ALS, and on therapy with riluzole (50 mg b.i.d.) for at least 3 months. The projected duration of treatment with pentoxifylline is 18 months.

[0227] The main efficacy endpoints are survival rate, quality of life and muscle tests.

[0228] Other aspects and applications of the invention concern:

[0229] use of all or part of a sequence derived from PDE4B messenger RNA for purposes of diagnosis or screening or characterisation of neurodegenerative diseases having a component or a stage related to the excitotoxicity phenomenon, such as Alzheimer's disease, Parkinson's disease, multiple sclerosis, Huntington's chorea, ALS or cerebral ischemia,

[0230] use of any nucleic acid fragment including antisense RNAs for purposes of inhibiting expression of PDE4B in patients with such diseases,

[0231] use of any chemical compound, particularly pentoxifylline, etazolate, or any pharmaceutical composition containing them, for purposes of inhibiting PDE4B activity in patients with such diseases,

[0232] use of all or part of a sequence derived from PDE4B messenger RNA for purposes of characterising tissue and the ischemic situation.

1 10 1 2912 DNA Mus musculus CDS (218)..(2383) 1 aaaggcagcc tgataaagct ccttgtgaca ggctgtcttg ccagtctccc agtatgctcc 60 tcttgctctg aagtgctcca ggattgaaac cacagcttcc caaattagcc tgggaagagt 120 gtgcggaccc agcagccttt taacccgcgt cagtgccttt gctatgttca agactgctgt 180 tttggatggt gaatgctagc tagcactcca tcgagac atg aca gca aaa aat tct 235 Met Thr Ala Lys Asn Ser 1 5 cca aaa gaa ttt act gct tcg gaa tct gag gtt tgc ata aag act ttc 283 Pro Lys Glu Phe Thr Ala Ser Glu Ser Glu Val Cys Ile Lys Thr Phe 10 15 20 aag gag cag atg cgc ttg gaa ctt gag ctt cca aag cta cca gga aac 331 Lys Glu Gln Met Arg Leu Glu Leu Glu Leu Pro Lys Leu Pro Gly Asn 25 30 35 aga cct aca tct ccc aaa att tct cca cgc agt tca cca agg aat tca 379 Arg Pro Thr Ser Pro Lys Ile Ser Pro Arg Ser Ser Pro Arg Asn Ser 40 45 50 cca tgc ttt ttc aga aag ttg ctg gtg aat aaa agc atc cga cag cgg 427 Pro Cys Phe Phe Arg Lys Leu Leu Val Asn Lys Ser Ile Arg Gln Arg 55 60 65 70 cgt cgc ttc acg gtg gct cat aca tgc ttt gat gtg gaa aat ggc cct 475 Arg Arg Phe Thr Val Ala His Thr Cys Phe Asp Val Glu Asn Gly Pro 75 80 85 tct cca ggt cgg agc cca ctg gac cct caa gcc ggc tct tcg tcg gga 523 Ser Pro Gly Arg Ser Pro Leu Asp Pro Gln Ala Gly Ser Ser Ser Gly 90 95 100 ctg gta ctt cat gcc gcc ttt cct ggg cac agc cag cgc agg gag tcg 571 Leu Val Leu His Ala Ala Phe Pro Gly His Ser Gln Arg Arg Glu Ser 105 110 115 ttc ctc tac gat ctt gac agc gac tat gac ttg tca cca aaa gcg atg 619 Phe Leu Tyr Asp Leu Asp Ser Asp Tyr Asp Leu Ser Pro Lys Ala Met 120 125 130 tcc agg aac tca tca ctt ccc agt gag caa cac ggc gat gac ctg att 667 Ser Arg Asn Ser Ser Leu Pro Ser Glu Gln His Gly Asp Asp Leu Ile 135 140 145 150 gtc act cct ttt gcc cag gtt ctt gcc agc ttg cga agt gta aga aac 715 Val Thr Pro Phe Ala Gln Val Leu Ala Ser Leu Arg Ser Val Arg Asn 155 160 165 aac ttc acc ctg ctg acg aac ctt cat gga gcg ccg aac aag agg tca 763 Asn Phe Thr Leu Leu Thr Asn Leu His Gly Ala Pro Asn Lys Arg Ser 170 175 180 cca gcg gct agt cag gct cca gtc tcc aga gtc agc ctg caa gag gaa 811 Pro Ala Ala Ser Gln Ala Pro Val Ser Arg Val Ser Leu Gln Glu Glu 185 190 195 tca tat cag aaa cta gca atg gag acg ctg gag gaa cta gac tgg tgc 859 Ser Tyr Gln Lys Leu Ala Met Glu Thr Leu Glu Glu Leu Asp Trp Cys 200 205 210 cta gac cag cta gag acc atc cag acc tac cgc tct gtc agc gag atg 907 Leu Asp Gln Leu Glu Thr Ile Gln Thr Tyr Arg Ser Val Ser Glu Met 215 220 225 230 gct tca aac aag ttc aaa agg atg ctg aac cgg gag ctg aca cac ctc 955 Ala Ser Asn Lys Phe Lys Arg Met Leu Asn Arg Glu Leu Thr His Leu 235 240 245 tca gag atg agc aga tca ggg aac cag gtg tct gag tac att tca aac 1003 Ser Glu Met Ser Arg Ser Gly Asn Gln Val Ser Glu Tyr Ile Ser Asn 250 255 260 acg ttc tta gac aag cag aac gat gtg gaa atc cca tct ccc acg cag 1051 Thr Phe Leu Asp Lys Gln Asn Asp Val Glu Ile Pro Ser Pro Thr Gln 265 270 275 aag gac agg gag aag aag aag aag cag cag ctc atg acc cag ata agt 1099 Lys Asp Arg Glu Lys Lys Lys Lys Gln Gln Leu Met Thr Gln Ile Ser 280 285 290 gga gtg aag aaa ctg atg cac agc tca agc ctg aac aac aca agc atc 1147 Gly Val Lys Lys Leu Met His Ser Ser Ser Leu Asn Asn Thr Ser Ile 295 300 305 310 tca cgc ttc ggg atc aac acg gaa aat gag gat cat cta gcc aag gag 1195 Ser Arg Phe Gly Ile Asn Thr Glu Asn Glu Asp His Leu Ala Lys Glu 315 320 325 ctg gaa gac ctg aac aaa tgg ggc ctt aac atc ttc aat gtg gct ggg 1243 Leu Glu Asp Leu Asn Lys Trp Gly Leu Asn Ile Phe Asn Val Ala Gly 330 335 340 tac tca cat aat cgg ccc ctt acg tgc atc atg tat gca ata ttc cag 1291 Tyr Ser His Asn Arg Pro Leu Thr Cys Ile Met Tyr Ala Ile Phe Gln 345 350 355 gaa aga gac ctt ctg aag acg ttt aaa atc tca tct gac acc ttt gta 1339 Glu Arg Asp Leu Leu Lys Thr Phe Lys Ile Ser Ser Asp Thr Phe Val 360 365 370 acc tac atg atg act tta gaa gac cat tac cat tct gat gtg gca tat 1387 Thr Tyr Met Met Thr Leu Glu Asp His Tyr His Ser Asp Val Ala Tyr 375 380 385 390 cac aac agc ctg cat gct gct gac gtg gcc cag tca act cac gtt ctc 1435 His Asn Ser Leu His Ala Ala Asp Val Ala Gln Ser Thr His Val Leu 395 400 405 ctt tct acg ccg gca ctg gat gct gtc ttc aca gac ctg gaa atc ctg 1483 Leu Ser Thr Pro Ala Leu Asp Ala Val Phe Thr Asp Leu Glu Ile Leu 410 415 420 gct gcc att ttt gca gct gcc atc cat gat gtc gat cat cct gga gtc 1531 Ala Ala Ile Phe Ala Ala Ala Ile His Asp Val Asp His Pro Gly Val 425 430 435 tcc aat cag ttt ctc atc aat aca aat tct gaa ctt gct ttg atg tat 1579 Ser Asn Gln Phe Leu Ile Asn Thr Asn Ser Glu Leu Ala Leu Met Tyr 440 445 450 aat gat gaa tct gtt ctg gaa aac cat cac ctt gct gtg gga ttc aaa 1627 Asn Asp Glu Ser Val Leu Glu Asn His His Leu Ala Val Gly Phe Lys 455 460 465 470 ttg cta caa gag gaa cac tgc gac atc ttt cag aat ctt acc aag aag 1675 Leu Leu Gln Glu Glu His Cys Asp Ile Phe Gln Asn Leu Thr Lys Lys 475 480 485 caa cgc cag aca ctc agg aaa atg gtg att gac atg gtg ttg gca act 1723 Gln Arg Gln Thr Leu Arg Lys Met Val Ile Asp Met Val Leu Ala Thr 490 495 500 gat atg tcc aaa cac atg agc ctc ctg gca gac ctt aaa aca atg gta 1771 Asp Met Ser Lys His Met Ser Leu Leu Ala Asp Leu Lys Thr Met Val 505 510 515 gaa acc aag aag gtg aca agc tcc ggt gtt ctc ctc ctg gac aac tat 1819 Glu Thr Lys Lys Val Thr Ser Ser Gly Val Leu Leu Leu Asp Asn Tyr 520 525 530 act gac cgg ata cag gtt ctt cgc aac atg gta cac tgt gca gac ctg 1867 Thr Asp Arg Ile Gln Val Leu Arg Asn Met Val His Cys Ala Asp Leu 535 540 545 550 agc aac ccc acc aag tcc ttg gaa ttg tat cgg caa tgg acc gat cgt 1915 Ser Asn Pro Thr Lys Ser Leu Glu Leu Tyr Arg Gln Trp Thr Asp Arg 555 560 565 atc atg gag gag ttt ttc cag cag gga gac aaa gaa cgg gag agg gga 1963 Ile Met Glu Glu Phe Phe Gln Gln Gly Asp Lys Glu Arg Glu Arg Gly 570 575 580 atg gag att agc cca atg tgt gat aag cac aca gct tct gtg gaa aaa 2011 Met Glu Ile Ser Pro Met Cys Asp Lys His Thr Ala Ser Val Glu Lys 585 590 595 tcc cag gtt ggt ttc att gac tac att gtc cat cca ctg tgg gag acc 2059 Ser Gln Val Gly Phe Ile Asp Tyr Ile Val His Pro Leu Trp Glu Thr 600 605 610 tgg gca gac ctg gtt caa ccg gat gct caa gat att ctg gat aca cta 2107 Trp Ala Asp Leu Val Gln Pro Asp Ala Gln Asp Ile Leu Asp Thr Leu 615 620 625 630 gaa gat aac agg aac tgg tac cag agt atg ata ccc cag agc cct tcc 2155 Glu Asp Asn Arg Asn Trp Tyr Gln Ser Met Ile Pro Gln Ser Pro Ser 635 640 645 ccg cca ctg gat gag agg agc agg gac tgc caa ggc ctg atg gag aag 2203 Pro Pro Leu Asp Glu Arg Ser Arg Asp Cys Gln Gly Leu Met Glu Lys 650 655 660 ttt cag ttt gaa ctg acc ctt gag gaa gag gat tct gag gga ccg gaa 2251 Phe Gln Phe Glu Leu Thr Leu Glu Glu Glu Asp Ser Glu Gly Pro Glu 665 670 675 aag gag gga gaa ggc cac agc tat ttc agc agc aca aag acg ctt tgt 2299 Lys Glu Gly Glu Gly His Ser Tyr Phe Ser Ser Thr Lys Thr Leu Cys 680 685 690 gtg att gat cca gag aac agg gat tct ctg gaa gag act gac ata gac 2347 Val Ile Asp Pro Glu Asn Arg Asp Ser Leu Glu Glu Thr Asp Ile Asp 695 700 705 710 att gca aca gaa gac aag tct ccg atc gac aca taa tctctctccc 2393 Ile Ala Thr Glu Asp Lys Ser Pro Ile Asp Thr 715 720 tctgtgtgga gatgaacatt ccacccttga ctgagcatgc ccgctgagtg gtagggtcac 2453 ctaccatggc caaggcctgc acaggacaaa ggccacctgg cctttccagt tacttgagtt 2513 tggagccaga atgccaggcc gtgaagcaaa tagcagttcc atgctgtctt gccttgcctg 2573 caagcttggc ggagacccgc agctgtatgt ggtagtagag gccagttccc atcaaagcta 2633 aaatggcttg aaaacagagg acacaaagct gagagattgc tctgcactag gtgttgggaa 2693 gctgtcctga cagatgactg aactcactaa caacttcatc tataaatctc accacccaac 2753 ccattgtctg ccaacctgtg tgcctttttt tgtaaaatgt tttcgcgtct ttgaaatgcc 2813 tgttgaatat ctagagttta gtaccaactt ctacaaactt ttttgagtct ttcttgaaaa 2873 acaaaaaaaa aaaaaaaaaa aaaaaaaaaa aaaaaaaaa 2912 2 721 PRT Mus musculus 2 Met Thr Ala Lys Asn Ser Pro Lys Glu Phe Thr Ala Ser Glu Ser Glu 1 5 10 15 Val Cys Ile Lys Thr Phe Lys Glu Gln Met Arg Leu Glu Leu Glu Leu 20 25 30 Pro Lys Leu Pro Gly Asn Arg Pro Thr Ser Pro Lys Ile Ser Pro Arg 35 40 45 Ser Ser Pro Arg Asn Ser Pro Cys Phe Phe Arg Lys Leu Leu Val Asn 50 55 60 Lys Ser Ile Arg Gln Arg Arg Arg Phe Thr Val Ala His Thr Cys Phe 65 70 75 80 Asp Val Glu Asn Gly Pro Ser Pro Gly Arg Ser Pro Leu Asp Pro Gln 85 90 95 Ala Gly Ser Ser Ser Gly Leu Val Leu His Ala Ala Phe Pro Gly His 100 105 110 Ser Gln Arg Arg Glu Ser Phe Leu Tyr Asp Leu Asp Ser Asp Tyr Asp 115 120 125 Leu Ser Pro Lys Ala Met Ser Arg Asn Ser Ser Leu Pro Ser Glu Gln 130 135 140 His Gly Asp Asp Leu Ile Val Thr Pro Phe Ala Gln Val Leu Ala Ser 145 150 155 160 Leu Arg Ser Val Arg Asn Asn Phe Thr Leu Leu Thr Asn Leu His Gly 165 170 175 Ala Pro Asn Lys Arg Ser Pro Ala Ala Ser Gln Ala Pro Val Ser Arg 180 185 190 Val Ser Leu Gln Glu Glu Ser Tyr Gln Lys Leu Ala Met Glu Thr Leu 195 200 205 Glu Glu Leu Asp Trp Cys Leu Asp Gln Leu Glu Thr Ile Gln Thr Tyr 210 215 220 Arg Ser Val Ser Glu Met Ala Ser Asn Lys Phe Lys Arg Met Leu Asn 225 230 235 240 Arg Glu Leu Thr His Leu Ser Glu Met Ser Arg Ser Gly Asn Gln Val 245 250 255 Ser Glu Tyr Ile Ser Asn Thr Phe Leu Asp Lys Gln Asn Asp Val Glu 260 265 270 Ile Pro Ser Pro Thr Gln Lys Asp Arg Glu Lys Lys Lys Lys Gln Gln 275 280 285 Leu Met Thr Gln Ile Ser Gly Val Lys Lys Leu Met His Ser Ser Ser 290 295 300 Leu Asn Asn Thr Ser Ile Ser Arg Phe Gly Ile Asn Thr Glu Asn Glu 305 310 315 320 Asp His Leu Ala Lys Glu Leu Glu Asp Leu Asn Lys Trp Gly Leu Asn 325 330 335 Ile Phe Asn Val Ala Gly Tyr Ser His Asn Arg Pro Leu Thr Cys Ile 340 345 350 Met Tyr Ala Ile Phe Gln Glu Arg Asp Leu Leu Lys Thr Phe Lys Ile 355 360 365 Ser Ser Asp Thr Phe Val Thr Tyr Met Met Thr Leu Glu Asp His Tyr 370 375 380 His Ser Asp Val Ala Tyr His Asn Ser Leu His Ala Ala Asp Val Ala 385 390 395 400 Gln Ser Thr His Val Leu Leu Ser Thr Pro Ala Leu Asp Ala Val Phe 405 410 415 Thr Asp Leu Glu Ile Leu Ala Ala Ile Phe Ala Ala Ala Ile His Asp 420 425 430 Val Asp His Pro Gly Val Ser Asn Gln Phe Leu Ile Asn Thr Asn Ser 435 440 445 Glu Leu Ala Leu Met Tyr Asn Asp Glu Ser Val Leu Glu Asn His His 450 455 460 Leu Ala Val Gly Phe Lys Leu Leu Gln Glu Glu His Cys Asp Ile Phe 465 470 475 480 Gln Asn Leu Thr Lys Lys Gln Arg Gln Thr Leu Arg Lys Met Val Ile 485 490 495 Asp Met Val Leu Ala Thr Asp Met Ser Lys His Met Ser Leu Leu Ala 500 505 510 Asp Leu Lys Thr Met Val Glu Thr Lys Lys Val Thr Ser Ser Gly Val 515 520 525 Leu Leu Leu Asp Asn Tyr Thr Asp Arg Ile Gln Val Leu Arg Asn Met 530 535 540 Val His Cys Ala Asp Leu Ser Asn Pro Thr Lys Ser Leu Glu Leu Tyr 545 550 555 560 Arg Gln Trp Thr Asp Arg Ile Met Glu Glu Phe Phe Gln Gln Gly Asp 565 570 575 Lys Glu Arg Glu Arg Gly Met Glu Ile Ser Pro Met Cys Asp Lys His 580 585 590 Thr Ala Ser Val Glu Lys Ser Gln Val Gly Phe Ile Asp Tyr Ile Val 595 600 605 His Pro Leu Trp Glu Thr Trp Ala Asp Leu Val Gln Pro Asp Ala Gln 610 615 620 Asp Ile Leu Asp Thr Leu Glu Asp Asn Arg Asn Trp Tyr Gln Ser Met 625 630 635 640 Ile Pro Gln Ser Pro Ser Pro Pro Leu Asp Glu Arg Ser Arg Asp Cys 645 650 655 Gln Gly Leu Met Glu Lys Phe Gln Phe Glu Leu Thr Leu Glu Glu Glu 660 665 670 Asp Ser Glu Gly Pro Glu Lys Glu Gly Glu Gly His Ser Tyr Phe Ser 675 680 685 Ser Thr Lys Thr Leu Cys Val Ile Asp Pro Glu Asn Arg Asp Ser Leu 690 695 700 Glu Glu Thr Asp Ile Asp Ile Ala Thr Glu Asp Lys Ser Pro Ile Asp 705 710 715 720 Thr 3 4068 DNA Homo sapiens CDS (766)..(2460) PDE4B 3 gaattcctcc tctcttcacc ccgttagctg ttttcaatgt aatgctgccg tccttctctt 60 gcactgcctt ctgcgctaac acctccattc ctgtttataa ccgtgtattt attacttaat 120 gtatataatg taatgttttg taagttatta atttatatat ctaacattgc ctgccaatgg 180 tggtgttaaa tttgtgtaga aaactctgcc taagagttac gactttttct tgtaatgttt 240 tgtattgtgt attatataac ccaaacgtca cttagtagag acatatggcc cccttggcag 300 agaggacagg ggtgggcttt tgttcaaagg gtctgccctt tccctgcctg agttgctact 360 tctgcacaac ccctttatga accagttttc acccgaattt tgactgtttc atttagaaga 420 aaagcaaaat gagaaaaagc tttcctcatt tctccttgag atggcaaagc actcagaaat 480 gacatcacat accctaaaga accctgggat gactaaggca gagagagtct gagaaaactc 540 tttggtgctt ctgcctttag ttttaggaca catttatgca gatgagctta taagagaccg 600 ttccctccgc cttcttcctc agaggaagtt tcttggtaga tcaccgacac ctcatccagg 660 cggggggttg gggggaaact tggcaccagc catcccaggc agagcaccac tgtgatttgt 720 tctcctggtg gagagagctg gaaggaagga gccagcgtgc aaata atg aag gag cac 777 Met Lys Glu His 1 ggg ggc acc ttc agt agc acc gga atc agc ggt ggt agc ggt gac tct 825 Gly Gly Thr Phe Ser Ser Thr Gly Ile Ser Gly Gly Ser Gly Asp Ser 5 10 15 20 gct atg gac agc ctg cag ccg ctc cag cct aac tac atg cct gtg tgt 873 Ala Met Asp Ser Leu Gln Pro Leu Gln Pro Asn Tyr Met Pro Val Cys 25 30 35 ttg ttt gca gaa gaa tct tat caa aaa tta gca atg gaa acg ctg gag 921 Leu Phe Ala Glu Glu Ser Tyr Gln Lys Leu Ala Met Glu Thr Leu Glu 40 45 50 gaa tta gac tgg tgt tta gac cag cta gag acc ata cag acc tac cgg 969 Glu Leu Asp Trp Cys Leu Asp Gln Leu Glu Thr Ile Gln Thr Tyr Arg 55 60 65 tct gtc agt gag atg gct tct aac aag ttc aaa aga atg ctg aac cgg 1017 Ser Val Ser Glu Met Ala Ser Asn Lys Phe Lys Arg Met Leu Asn Arg 70 75 80 gag ctg aca cac ctc tca gag atg agc cga tca ggg aac cag gtg tct 1065 Glu Leu Thr His Leu Ser Glu Met Ser Arg Ser Gly Asn Gln Val Ser 85 90 95 100 gaa tac att tca aat act ttc tta gac aag cag aat gat gtg gag atc 1113 Glu Tyr Ile Ser Asn Thr Phe Leu Asp Lys Gln Asn Asp Val Glu Ile 105 110 115 cca tct cct acc cag aaa gac agg gag aaa aag aaa aag cag cag ctc 1161 Pro Ser Pro Thr Gln Lys Asp Arg Glu Lys Lys Lys Lys Gln Gln Leu 120 125 130 atg acc cag ata agt gga gtg aag aaa tta atg cat agt tca agc cta 1209 Met Thr Gln Ile Ser Gly Val Lys Lys Leu Met His Ser Ser Ser Leu 135 140 145 aac aat aca agc atc tca cgc ttt gga gtc aac act gaa aat gaa gat 1257 Asn Asn Thr Ser Ile Ser Arg Phe Gly Val Asn Thr Glu Asn Glu Asp 150 155 160 cac ctg gcc aag gag ctg gaa gac ctg aac aaa tgg ggt ctt aac atc 1305 His Leu Ala Lys Glu Leu Glu Asp Leu Asn Lys Trp Gly Leu Asn Ile 165 170 175 180 ttt aat gtg gct gga tat tct cac aat aga ccc cta aca tgc atc atg 1353 Phe Asn Val Ala Gly Tyr Ser His Asn Arg Pro Leu Thr Cys Ile Met 185 190 195 tat gct ata ttc cag gaa aga gac ctc cta aag aca ttc aga atc tca 1401 Tyr Ala Ile Phe Gln Glu Arg Asp Leu Leu Lys Thr Phe Arg Ile Ser 200 205 210 tct gac aca ttt ata acc tac atg atg act tta gaa gac cat tac cat 1449 Ser Asp Thr Phe Ile Thr Tyr Met Met Thr Leu Glu Asp His Tyr His 215 220 225 tct gac gtg gca tat cac aac agc ctg cac gct gct gat gta gcc cag 1497 Ser Asp Val Ala Tyr His Asn Ser Leu His Ala Ala Asp Val Ala Gln 230 235 240 tcg acc cat gtt ctc ctt tct aca cca gca tta gac gct gtc ttc aca 1545 Ser Thr His Val Leu Leu Ser Thr Pro Ala Leu Asp Ala Val Phe Thr 245 250 255 260 gat ttg gag atc ctg gct gcc att ttt gca gct gcc atc cat gac gtt 1593 Asp Leu Glu Ile Leu Ala Ala Ile Phe Ala Ala Ala Ile His Asp Val 265 270 275 gat cat cct gga gtc tcc aat cag ttt ctc atc aac aca aat tca gaa 1641 Asp His Pro Gly Val Ser Asn Gln Phe Leu Ile Asn Thr Asn Ser Glu 280 285 290 ctt gct ttg atg tat aat gat gaa tct gtg ttg gaa aat cat cac ctt 1689 Leu Ala Leu Met Tyr Asn Asp Glu Ser Val Leu Glu Asn His His Leu 295 300 305 gct gtg ggt ttc aaa ctg ctg caa gaa gaa cac tgt gac atc ttc atg 1737 Ala Val Gly Phe Lys Leu Leu Gln Glu Glu His Cys Asp Ile Phe Met 310 315 320 aat ctc acc aag aag cag cgt cag aca ctc agg aag atg gtt att gac 1785 Asn Leu Thr Lys Lys Gln Arg Gln Thr Leu Arg Lys Met Val Ile Asp 325 330 335 340 atg gtg tta gca act gat atg tct aaa cat atg agc ctg ctg gca gac 1833 Met Val Leu Ala Thr Asp Met Ser Lys His Met Ser Leu Leu Ala Asp 345 350 355 ctg aag aca atg gta gaa acg aag aaa gtt aca agt tca ggc gtt ctt 1881 Leu Lys Thr Met Val Glu Thr Lys Lys Val Thr Ser Ser Gly Val Leu 360 365 370 ctc cta gac aac tat acc gat cgc att cag gtc ctt cgc aac atg gta 1929 Leu Leu Asp Asn Tyr Thr Asp Arg Ile Gln Val Leu Arg Asn Met Val 375 380 385 cac tgt gca gac ctg agc aac ccc acc aag tcc ttg gaa ttg tat cgg 1977 His Cys Ala Asp Leu Ser Asn Pro Thr Lys Ser Leu Glu Leu Tyr Arg 390 395 400 caa tgg aca gac cgc atc atg gag gaa ttt ttc cag cag gga gac aaa 2025 Gln Trp Thr Asp Arg Ile Met Glu Glu Phe Phe Gln Gln Gly Asp Lys 405 410 415 420 gag cgg gag agg gga atg gaa att agc cca atg tgt gat aaa cac aca 2073 Glu Arg Glu Arg Gly Met Glu Ile Ser Pro Met Cys Asp Lys His Thr 425 430 435 gct tct gtg gaa aaa tcc cag gtt ggt ttc atc gac tac att gtc cat 2121 Ala Ser Val Glu Lys Ser Gln Val Gly Phe Ile Asp Tyr Ile Val His 440 445 450 cca ttg tgg gag aca tgg gca gat ttg gta cag cct gat gct cag gac 2169 Pro Leu Trp Glu Thr Trp Ala Asp Leu Val Gln Pro Asp Ala Gln Asp 455 460 465 att ctc gat acc tta gaa gat aac agg aac tgg tat cag agc atg ata 2217 Ile Leu Asp Thr Leu Glu Asp Asn Arg Asn Trp Tyr Gln Ser Met Ile 470 475 480 cct caa agt ccc tca cca cca ctg gac gag cag aac agg gac tgc cag 2265 Pro Gln Ser Pro Ser Pro Pro Leu Asp Glu Gln Asn Arg Asp Cys Gln 485 490 495 500 ggt ctg atg gag aag ttt cag ttt gaa ctg act ctc gat gag gaa gat 2313 Gly Leu Met Glu Lys Phe Gln Phe Glu Leu Thr Leu Asp Glu Glu Asp 505 510 515 tct gaa gga cct gag aag gag gga gag gga cac agc tat ttc agc agc 2361 Ser Glu Gly Pro Glu Lys Glu Gly Glu Gly His Ser Tyr Phe Ser Ser 520 525 530 aca aag acg ctt tgt gtg att gat cca gaa aac aga gat tcc ctg gga 2409 Thr Lys Thr Leu Cys Val Ile Asp Pro Glu Asn Arg Asp Ser Leu Gly 535 540 545 gag act gac ata gac att gca aca gaa gac aag tcc ccc gtg gat aca 2457 Glu Thr Asp Ile Asp Ile Ala Thr Glu Asp Lys Ser Pro Val Asp Thr 550 555 560 taa tccccctctc cctgtggaga tgaacattct atccttgatg agcatgccag 2510 ctatgtggta gggccagccc accatggggg ccaagacctg cacaggacaa gggccacctg 2570 gcctttcagt tacttgagtt tggagtcaga aagcaagacc aggaagcaaa tagcagctca 2630 ggaaatccca cggttgactt gccttgatgg caagcttggt ggagagggct gaagctgttg 2690 ctgggggccg attctgatca agacacatgg cttgaaaatg gaagacacaa aactgagaga 2750 tcattctgca ctaagtttcg ggaacttatc cccgacagtg actgaactca ctgactaata 2810 acttcattta tgaatcttct cacttgtccc tttgtctgcc aacctgtgtg ccttttttgt 2870 aaaacatttt catgtcttta aaatgcctgt tgaatacctg gagtttagta tcaacttcta 2930 cacagataag ctttcaaagt tgacaaactt ttttgactct ttctggaaaa gggaaagaaa 2990 atagtcttcc ttctttcttg ggcaatatcc ttcactttac tacagttact tttgcaaaca 3050 gacagaaagg atacacttct aaccacattt tacttccttc ccctgttgtc cagtccaact 3110 ccacagtcac tcttaaaact tctctctgtt tgcctgcctc caacagtact tttaactttt 3170 tgctgtaaac agaataaaat tgaacaaatt agggggtaga aaggagcagt ggtgtcgttc 3230 accgtgagag tctgcataga actcagcagt gtgccctgct gtgtcttgga ccctgccccc 3290 cacaggagtt gctacagtcc ctggccctgc ttcccatcct cctctcttca ccccgttagc 3350 tgttttcaat gtaatgctgc cgtccttctc ttgcactgcc ttctgcgcta acacctccat 3410 tcctgtttat aaccgtgtat ttattactta atgtatataa tgtaatgttt tgtaagttat 3470 taatttatat atctaacatt gcctgccaat ggtggtgtta aatttgtgta gaaaactctg 3530 cctaagagtt acgacttttt cttgtaatgt tttgtattgt gtattatata acccaaacgt 3590 cacttagtag agacatatgg cccccttggc agagaggaca ggggtgggct tttgttcaaa 3650 gggtctgccc tttccctgcc tgagttgcta cttctgcaca acccctttat gaaccagttt 3710 tggaaacaat attctcacat tagatactaa atggtttata ctgagtcttt tacttttgta 3770 tagcttgata ggggcagggg caatgggatg tagtttttac ccaggttcta tccaaatcta 3830 tgtgggcatg agttgggtta taactggatc ctactatcat tgtggctttg gttcaaaagg 3890 aaacactaca tttgctcaca gatgattctt ctgattcttc tgaatgctcc cgaactactg 3950 actttgaaga ggtagcctcc tgcctgccat taagcaggaa tgtcatgttc cagttcatta 4010 caaaagaaaa caataaaaca atgtgaattt ttataataaa aaaaaaaaaa aggaattc 4068 4 564 PRT Homo sapiens 4 Met Lys Glu His Gly Gly Thr Phe Ser Ser Thr Gly Ile Ser Gly Gly 1 5 10 15 Ser Gly Asp Ser Ala Met Asp Ser Leu Gln Pro Leu Gln Pro Asn Tyr 20 25 30 Met Pro Val Cys Leu Phe Ala Glu Glu Ser Tyr Gln Lys Leu Ala Met 35 40 45 Glu Thr Leu Glu Glu Leu Asp Trp Cys Leu Asp Gln Leu Glu Thr Ile 50 55 60 Gln Thr Tyr Arg Ser Val Ser Glu Met Ala Ser Asn Lys Phe Lys Arg 65 70 75 80 Met Leu Asn Arg Glu Leu Thr His Leu Ser Glu Met Ser Arg Ser Gly 85 90 95 Asn Gln Val Ser Glu Tyr Ile Ser Asn Thr Phe Leu Asp Lys Gln Asn 100 105 110 Asp Val Glu Ile Pro Ser Pro Thr Gln Lys Asp Arg Glu Lys Lys Lys 115 120 125 Lys Gln Gln Leu Met Thr Gln Ile Ser Gly Val Lys Lys Leu Met His 130 135 140 Ser Ser Ser Leu Asn Asn Thr Ser Ile Ser Arg Phe Gly Val Asn Thr 145 150 155 160 Glu Asn Glu Asp His Leu Ala Lys Glu Leu Glu Asp Leu Asn Lys Trp 165 170 175 Gly Leu Asn Ile Phe Asn Val Ala Gly Tyr Ser His Asn Arg Pro Leu 180 185 190 Thr Cys Ile Met Tyr Ala Ile Phe Gln Glu Arg Asp Leu Leu Lys Thr 195 200 205 Phe Arg Ile Ser Ser Asp Thr Phe Ile Thr Tyr Met Met Thr Leu Glu 210 215 220 Asp His Tyr His Ser Asp Val Ala Tyr His Asn Ser Leu His Ala Ala 225 230 235 240 Asp Val Ala Gln Ser Thr His Val Leu Leu Ser Thr Pro Ala Leu Asp 245 250 255 Ala Val Phe Thr Asp Leu Glu Ile Leu Ala Ala Ile Phe Ala Ala Ala 260 265 270 Ile His Asp Val Asp His Pro Gly Val Ser Asn Gln Phe Leu Ile Asn 275 280 285 Thr Asn Ser Glu Leu Ala Leu Met Tyr Asn Asp Glu Ser Val Leu Glu 290 295 300 Asn His His Leu Ala Val Gly Phe Lys Leu Leu Gln Glu Glu His Cys 305 310 315 320 Asp Ile Phe Met Asn Leu Thr Lys Lys Gln Arg Gln Thr Leu Arg Lys 325 330 335 Met Val Ile Asp Met Val Leu Ala Thr Asp Met Ser Lys His Met Ser 340 345 350 Leu Leu Ala Asp Leu Lys Thr Met Val Glu Thr Lys Lys Val Thr Ser 355 360 365 Ser Gly Val Leu Leu Leu Asp Asn Tyr Thr Asp Arg Ile Gln Val Leu 370 375 380 Arg Asn Met Val His Cys Ala Asp Leu Ser Asn Pro Thr Lys Ser Leu 385 390 395 400 Glu Leu Tyr Arg Gln Trp Thr Asp Arg Ile Met Glu Glu Phe Phe Gln 405 410 415 Gln Gly Asp Lys Glu Arg Glu Arg Gly Met Glu Ile Ser Pro Met Cys 420 425 430 Asp Lys His Thr Ala Ser Val Glu Lys Ser Gln Val Gly Phe Ile Asp 435 440 445 Tyr Ile Val His Pro Leu Trp Glu Thr Trp Ala Asp Leu Val Gln Pro 450 455 460 Asp Ala Gln Asp Ile Leu Asp Thr Leu Glu Asp Asn Arg Asn Trp Tyr 465 470 475 480 Gln Ser Met Ile Pro Gln Ser Pro Ser Pro Pro Leu Asp Glu Gln Asn 485 490 495 Arg Asp Cys Gln Gly Leu Met Glu Lys Phe Gln Phe Glu Leu Thr Leu 500 505 510 Asp Glu Glu Asp Ser Glu Gly Pro Glu Lys Glu Gly Glu Gly His Ser 515 520 525 Tyr Phe Ser Ser Thr Lys Thr Leu Cys Val Ile Asp Pro Glu Asn Arg 530 535 540 Asp Ser Leu Gly Glu Thr Asp Ile Asp Ile Ala Thr Glu Asp Lys Ser 545 550 555 560 Pro Val Asp Thr 5 20 DNA Artificial Sequence Description of Artificial Sequence primer 5 gccaggccgt gaagcaaata 20 6 18 DNA artificial sequence Description of Artificial Sequence primer 6 tcaaagacgc gaaaacat 18 7 21 DNA artificial sequence Description of Artificial Sequence primer 7 ccgcgtcagt gcctttgcta t 21 8 23 DNA artificial sequence Description of Artificial Sequence primer 8 cgctgtcgga tgcttttatt cac 23 9 19 DNA artificial sequence Description of Artificial Sequence primer 9 tcgctttctg gagggtgtc 19 10 18 DNA artificial sequence Description of Artificial Sequence primer 10 ccgcaggggc agcagtgg 18 

1-19. canceled.
 20. A method for detecting a situation of excitotoxicity or neuronal stress in a subject, comprising measuring in vitro the expression of phosphodiesterase 4, particularly phosphodiesterase 4B, in a sample from the subject.
 21. A method according to claim 20, comprising detecting the presence of a mutant RNA of phosphodiesterase 4, particularly phosphodiesterase 4B, in a sample from the subject, in particular a form deleted of all or part of the 3′ noncoding region.
 22. A method according to claim 20, comprising the placing in contact in vitro of a biological sample from a subject, containing a nucleic acid, with a nucleic acid comprising all or part of a sequence derived from the PDE4B messenger RNA or gene, and detecting the formation of a hybrid.
 23. A method according to claim 20, comprising the placing in contact in vitro of a biological sample from a subject, containing a nucleic acid, with a nucleic acid comprising all or part of a sequence derived from the PDE4B messenger RNA or gene and wherein the sample comprises nerve or muscle cells.
 24. A method according to claim 20, for the diagnosis or detection of Alzheimer's disease, Parkinson's disease, multiple sclerosis, Huntington's chorea, ALS or cerebral ischemia.
 25. A method for the treatment of diseases associated with neuronal stress, particularly excitotoxicity, comprising administering to a subject in need of such treatment a compound that inhibits PDE4B activity or expression, preferably a compound that selectively inhibits PDE4.
 26. A method according to claim 25, wherein the neuronal excitotoxicity is associated with a neurodegenerative disease.
 27. A method according to claim 25, wherein the compound is an antisense nucleic acid, capable of inhibiting transcription of the PDE4B gene or translation of the corresponding messenger.
 28. A method according to claim 25, wherein the compound is a chemical compound of natural or synthetic origin.
 29. A method according to claim 25, wherein the compound is chosen from among the compounds in the pyrazolopyridine family, particularly etazolate, and the compounds in the family of xanthine derivatives, particularly pentoxifylline.
 30. A method according to claim 25, to inhibit or reduce neuronal excitotoxicity in the early stage of neurodegenerative diseases.
 31. A method according to claim 25, to improve neuron survival in patients with ALS.
 32. A method according to claim 25, for the treatment of Alzheimer's disease, Parkinson's disease, multiple sclerosis, Huntington's chorea or cerebral ischemia.
 33. A method according to claim 25, for the treatment of ALS, particularly to reduce neuronal excitotoxicity in the early stage of ALS.
 34. A method according to claim 25, wherein the compound is pentoxifylline.
 35. A method according to claim 34, to increase neuron survival in patients with ALS.
 36. A method according to claim 25, wherein the compound is etazolate.
 37. A method according to claim 36, to increase neuron survival in patients with ALS.
 38. A method according to claim 25, wherein the compound is selected from the group consisting of: 4-butylamino-1-ethyl-6-methyl-1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid ethyl ester (tracazolate), 4-butylamino-1-ethyl-1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid ethyl ester, 1-(4-amino-pyrazolo[3,4-b]pyridin-1-yl)-□-D-1-deoxy-ribofuranose, 1-ethyl-4-(N′-isopropylidene-hydrazino)-1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid ethyl ester (SQ 20009), 4-amino-6-methyl-1-n-pentyl-1H-pyrazolo[3,4-b]pyridine, 4-amino-1-ethyl-6-methyl-1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid ethyl ester (desbutyl tracacolate), 4-amino-1-pentyl-1H-pyrazolo[3,4-b]pyridine-5-carboxamide, 1-ethyl-6-methyl-4-methylamino-1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid ethyl ester, 4-amino-6-methyl-1-propyl-1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid ethyl ester, 1-ethyl-4-ethylamino-6-methyl-1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid ethyl ester, 4-amino-1-butyl-6-methyl-1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid ethyl ester, 5-(4-amino-pyrazolo[3,4-b]pyridin-1-yl)-2-hydroxymethyl-tetrahydro-furan-3-ol, 1-allyl-4-amino-6-methyl-1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid allyl ester, 4-amino-6-methyl-1-pentyl-1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid, 4-amino-1-ethyl-3,6-dimethyl-1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid ethyl ester, 4-dimethylamino-1-ethyl-6-methyl-1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid ethyl ester, 1-ethyl-6-methyl-4-propylamino-1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid ethyl ester, 4-amino-1-pentyl-1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid ethyl ester, 4-amino-6-methyl-1-pent-4-ynyl-1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid ethyl ester, 4-amino-1-but-3-enyl-1H-pyrazolo[3,4-b]pyridine-5-allylamide, 4-amino-1-pentyl-1H-pyrazolo[3,4-b]pyridine-5-isopropylamide, 4-amino-1-pentyl-N-n-propyl-1H-pyrazolo-[3,4-b]pyridine-5-carboxamide, 4-amino-1-butyl-6-methyl-1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid allyl ester, 4-amino-6-methyl-1-pent-3-ynyl-1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid ethyl ester, 4-amino-1-pentyl-1H-pyrazolo[3,4-b]pyridine-5-prop-2-ynylamide, 4-amino-1-(3-methyl-butyl)-1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid allyl ester, 4-amino-1-pentyl-1H-pyrazolo<3,4-b>pyridine-5-N-(2-propenyl)carboxamide, 4-amino-1-pentyl-1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid allyl ester, 4-amino-1-pentyl-1H-pyrazolo[3,4-b]pyridine-5-butylamide, 4-amino-1-but-3-ynyl-6-methyl-1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid allyl ester, 4-amino-1-but-3-enyl-6-methyl-1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid allyl ester, 4-amino-6-methyl-1-pentyl-1H-pyrazolo[3,4-b]pyridine-5-allylamide, 4-amino-6-methyl-1-pentyl-1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid allyl ester, 4-amino-6-methyl-1-(3-methyl-butyl)-1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid allyl ester, 4-amino-6-methyl-1-pentyl-1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid isobutyl ester, 4-amino-6-methyl-1-pentyl-1H-pyrazolo[3,4-b]pyridine-5-butylamide, 4-amino-6-methyl-1-(3-methyl-but-2-enyl)-1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid allyl ester, 4-amino-1-pentyl-1H-pyrazolo[3,4-b]pyridine-5-cyclopropylamide, ethyl 4-amino-1-pentyl-1H-pyrazolo[3,4-b]pyridine-5-hydroxamate, 4-amino-6-methyl-1-pentyl-1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid prop-2-ynyl ester, 4-amino-6-methyl-1-pent-4-ynyl-1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid allyl ester, 4-amino-6-methyl-1-pent-4-enyl-1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid allyl ester, 4-amino-1-pent-3-ynyl-1H-pyrazolo[3,4-b]pyridine-5-propylamide, 4-amino-1-pentyl-1H-pyrazolo[3,4-b]pyridine-5-cyclopropylmethyl-amide, 4-amino-6-methyl-1-pentyl-1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid 2-methyl-allyl ester, 4-amino-1-pent-3-ynyl-1H-pyrazolo[3,4-b]pyridine-5-allylamide (ICI 190,622), 4-amino-1-pent-4-ynyl-N-2-propenyl-1H-pyrazolo[3,4-b]pyridine-5-carboxamide, 4-amino-1-pent-3-ynyl-1H-pyrazolo[3,4-b]pyridine-5-prop-2-ynylamide, 4-amino-1-pentyl-1H-pyrazolo[3,4-b]pyridine-5-but-2-ynylamide, 4-amino-6-methyl-1-pent-3-ynyl-1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid allyl ester, 4-amino-1-(2-cyclopropyl-ethyl)-6-methyl-1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid allyl ester, 4-amino-1-hex-5-ynyl-6-methyl-1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid allyl ester, 4-amino-1-pent-3-ynyl-1H-pyrazolo[3,4-b]pyridine-5-cyclopropylmethyl-amide, 4-amino-6-methyl-1-pentyl-1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid but-3-enyl ester, 4-amino-6-methyl-1-pentyl-1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid cyclopropylmethyl ester, 4-butylamino-1-pentyl-1H-pyrazolo[3,4-b]pyridine-5-allylamide, 4-amino-6-methyl-1-pentyl-1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid 2-cyclopropyl-ethyl ester, 4-amino-6-methyl-1-pent-3-ynyl-1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid cyclopropylmethyl ester, 4-amino-6-methyl-1-pent-4-ynyl-1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid cyclopropylmethyl ester, 4-amino-1-benzyl-6-methyl-1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid ethyl ester, 4-amino-1-pentyl-1H-pyrazolo[3,4-b]pyridine-5-benzylamide, 4-amino-1-pentyl-1H-pyrazolo[3,4-b]pyridine-5-phenylamide, 4-amino-6-methyl-1-pentyl-1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid benzyl ester, 4-azido-1-□-D-ribofuranosylpyrazolo[3,4-b]pyridine, 1-pent-3-ynyl-N-2-propenyl-4-propionamido-1 H-pyrazolo[3,4-b]pyridine-5-carboxamide, 2-(4-amino-pyrazolo[3,4-b]pyridin-1-yl)-5-hydroxymethyl-tetrahydro-furan-3,4-diol, 2-(6-methyl-1H-pyrazolo[3,4-b]pyridin-4-ylamino)-ethanol, 3-(6-methyl-1H-pyrazolo[3,4-b]pyridin-4-ylamino)-propan-1-ol, 3-(6-methyl-1H-pyrazolo[3,4-b]pyridin-4-ylamino)-acetic acid propyl ester, 2-(6-methyl-1H-pyrazolo[3,4-b]pyridin-4-ylamino)-propionic acid ethyl ester, 2-(6-methyl-1H-pyrazolo[3,4-b]pyridin-4-ylamino)-pentanoic acid ethyl ester, 2-(6-methyl-1H-pyrazolo[3,4-b]pyridin-4-ylamino)-benzoic acid ethyl ester, 3-(6-methyl-1H-pyrazolo[3,4-b]pyridin-4-ylamino)-pentanoic acid propyl ester, N-benzylidene-N′-(3-methyl-1-phenyl-1H-pyrazolo[3,4-b]pyridin-4-yl)-hydrazine, N-furan-2-ylmethylene-N′-(3-methyl-1-phenyl-1H-pyrazolo[3,4-b]pyridin-4-yl)-hydrazine, N-(4-fluoro-benzylidene)-N′-(3-methyl-1-phenyl-1H-pyrazolo[3,4-b]pyridin-4-yl)-hydrazine, N-(3-furan-2-yl-allylidene)-N′-(3-methyl-1-phenyl-1H-pyrazolo[3,4-b]pyridin-4-yl)-hydrazine, N-(4-methoxy-benzylidene)-N′-(3-methyl-1-phenyl-1H-pyrazolo[3,4-b]pyridin-4-yl)-hydrazine, 4-[(3-methyl-1-phenyl-1H-pyrazolo[3,4-b]pyridin-4-yl)-hydrazonomethyl]-benzonitrile, N-benzo[1,3]dioxol-5-ylmethylene-N′-(3-methyl-1-phenyl-1H-pyrazolo[3,4-b]pyridin-4-yl)-hydrazine, N-(3-methyl-1-phenyl-1H-pyrazolo[3,4-b]pyridin-4-yl)-N′-(4-nitro-benzylidene)-hydrazine, N-(3-methyl-1-phenyl-1H-pyrazolo[3,4-b]pyridin-4-yl)-N′-(2-nitro-benzylidene)-hydrazine, N-(3-methyl-1-phenyl-1H-pyrazolo[3,4-b]pyridin-4-yl)-N′-(4-trifluoromethyl-benzylidene)-hydrazine, N-(3-methyl-1-phenyl-1H-pyrazolo[3,4-b]pyridin-4-yl)-N′-(5-nitro-furan-2-ylmethylene)-hydrazine, N-(3-methyl-1-phenyl-1H-pyrazolo[3,4-b]pyridin-4-yl)-N′-(2-trifluoromethyl-benzylidene)-hydrazine, N-(3-methyl-1-phenyl-1H-pyrazolo[3,4-b]pyridin-4-yl)-N′-(6-nitro-benzo[1,3]dioxol-5-ylmethylene)-hydrazine, 4-(3-chloro-4-methoxy-benzylamino)-1-ethyl-1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid, 4-(3-chloro-4-methoxy-benzylamino)-1-ethyl-1H-pyrazolo[3,4-b]pyridine-5-(pyridin-4-ylmethyl)-amide, 4-(3-chloro-4-methoxy-benzylamino)-1-ethyl-1H-pyrazolo[3,4-b]pyridine-5-(tetrahydro-furan-2-ylmethyl)-amide, 4-(3-chloro-4-methoxy-benzylamino)-1-ethyl-1H-pyrazolo[3,4-b]pyridine-5-(5-hydroxy-pentyl)-amide, 4-(3-chloro-4-methoxy-benzylamino)-1-ethyl-1H-pyrazolo[3,4-b]pyridine-5-[3-(2-oxo-pyrrolidin-1-yl)-propyl]-amide, 4-tert-butylamino-1-(2-chloro-2-phenyl-ethyl)-1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid ethyl ester, 1-(2-chloro-2-phenyl-ethyl)-4-cyclopropylamino-1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid ethyl ester, 1-(2-chloro-2-phenyl-ethyl)-4-propylamino-1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid ethyl ester, 1-(2-chloro-2-phenyl-ethyl)-4-phenylamino-1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid ethyl ester, 4-butylamino-1-(2-chloro-2-phenyl-ethyl)-1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid ethyl ester, 1-(2-chloro-2-phenyl-ethyl)-4-(2-ethoxy-ethylamino)-1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid ethyl ester, 4-benzylamino-1-(2-chloro-2-phenyl-ethyl)-1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid ethyl ester, and 1-(2-chloro-2-phenyl-ethyl)-4-phenethylamino-1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid ethyl ester.
 39. A method according to claim 25, wherein the compound is a PDE4 inhibitor compound belonging to the pyrazolopyridine family, to increase neuron survival in patients with ALS.
 40. Nucleotide primer, wherein it is composed of a fragment of 8 to 20 consecutive residues from the sequence located between nucleotides 2384 and 2869 of sequence SEQ ID NO: 1 or between nucleotides 2461 and 4068 of the sequence SEQ ID NO: 3 or a sequence complementary thereto.
 41. Kit for analysing PDE4 expression, particularly differential expression between the 3′ noncoding region and the coding region, the kit comprising a nucleotide probe specific of part of the sequence of the 3′ noncoding region and a nucleotide probe specific of part of the sequence of the coding region.
 42. Kit for analysing PDE4 expression, particularly differential expression between the 3′ noncoding region and the coding region, the kit comprising a pair of nucleotide primers allowing specific amplification of at least part of the 3′ noncoding region of PDE4 and a pair of nucleotide primers allowing specific amplification of at least part of the PDE4 coding region. 